Tools for Student
313 hand-picked tools for Student. Free, private, browser-based.
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24-Point Solver & Game
24-point solver and game — enter 4 numbers and get every solution instantly, or play random hands against the clock.
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A1C to Blood Glucose Calculator
A1C ⇄ estimated average glucose, both ways, mg/dL or mmol/L, with the ADA range — educational, browser-only
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Chinese Acupoint Locator
200+ meridian acupoints / WHO 2008 standard locations / with contraindications, manipulation, and combinations.
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Add Days to Date Calculator
Add or subtract days, weeks, months, and years from any date — plus a business-day mode that skips weekends. Runs entirely in your browser.
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Affine Cipher Encoder & Decoder
Encrypt and decrypt the ax+b affine cipher with live modular-inverse check, browser-only
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Age Calculator
Calculate your exact age — years, months, days, hours. Compare two dates or count to a future date.
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Anagram Solver
Check if two words are anagrams, rearrange a set of letters into every ordering, and read the sorted letter fingerprint, all in your browser
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Angle Converter
Degrees, radians, gradians, turns, arcminutes, arcseconds and NATO mils, all from one input, copyable, browser-only
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Annulus Area Calculator
Area between two concentric circles — A = π(R² − r²), ring width, inner and outer circumference, solve backwards from area — browser-only
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Arabic 1100 Essential Words
Arabic 1100 essential A1–A2 MSA words — Arabic script with full ḥarakāt, DIN 31635 romanization, gender, three-form verbs, audio TTS.
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Arithmetic Sequence Calculator
Arithmetic sequence calculator — nth term, sum of the first n terms, and the common difference from any two terms, all in your browser.
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Armstrong Number Checker
Test if a number equals the sum of its digits each raised to the digit count (153 = 1^3 + 5^3 + 3^3), with full breakdown and a range list. Browser-only.
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Atbash Cipher
Mirror the alphabet, A↔Z B↔Y, no key, self-reciprocal so the same button encodes and decodes, browser-only
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Atom Economy Calculator
product molar mass ÷ Σ reactant molar masses × 100 — green-chemistry atom efficiency, with how it differs from percent yield — browser-only
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Blood Alcohol Content (BAC) Calculator
Widmark-formula BAC estimate from drinks, body weight, sex and time — educational only, never a fit-to-drive verdict — browser-only
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Bacon Cipher Encoder & Decoder
Turn text into five-letter A/B groups, or read a Baconian message back — 24 and 26 letter alphabets, custom symbols, browser only
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Number Base Converter
Number base converter — binary, octal, decimal, hex, and any base 2-36. Bitwise too.
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BaZi (Four Pillars) Calculator
BaZi (Four Pillars) calculator — Chinese metaphysics birth chart with 8 characters, five elements analysis.
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BCD Converter
Decimal ⇄ binary coded decimal in 8421 code, with packed view, hex and per-digit nibbles, all in your browser
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Beaufort Cipher
C = (key − text) mod 26, reciprocal — one keyword both encrypts and decrypts — browser-only
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Binary Calculator
Add, subtract, multiply and divide two binary numbers, exact BigInt math, results in binary, decimal, hex and octal, browser-only
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Binomial Expansion Calculator
Expand (a + b)ⁿ term by term with exact BigInt coefficients, substitute numbers like (2x + 3)⁴, and pull out any single term — browser-only
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Bionic Reading Converter
Bold the leading letters of every word — live preview, adjustable strength, export HTML — 100% in-browser
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Birthday Paradox Calculator
Birthday paradox calculator — see the probability of shared birthdays in a group of N people, visualized step by step.
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Blood Pressure Category Checker
Enter systolic and diastolic, see your AHA category on a color scale — Normal to Crisis, education only, runs in your browser
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BMI Calculator
Body Mass Index calculator with WHO + Asian classifications — metric and imperial — browser-only
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BMR Calculator
BMR calculator — basal metabolic rate by Mifflin-St Jeor and Harris-Benedict (compared side-by-side).
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Body Fat Calculator
Body fat % calculator — 4 formulas (US Navy / BMI-based / YMCA / Jackson-Pollock) with body shape visualization.
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Body Surface Area (BSA) Calculator
Four formulas side by side — Mosteller, DuBois, Haycock, Gehan-George — cm/kg or in/lb, one-click copy, browser-only
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BPM Tap Counter
BPM tap counter — tap the spacebar to the beat, instantly get tempo with running average, find your song's tempo for DJ / dance / metronome.
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Buoyancy Force Calculator
F = ρ·V·g · Archimedes' principle · will it float or sink · fresh/sea water + air presets · apparent weight · 100% browser-only
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Caesar Cipher Encoder & Decoder
Encrypt, decrypt and brute-force a Caesar shift cipher — all 25 shifts at once, ROT13 shortcut, browser-only
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Caffeine Calculator
Track how much caffeine is still in your system, how much is left at bedtime, and when it drops to a sleep-friendly level — half-life model, browser-only.
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Calorie Calculator
Calorie calculator — daily calorie needs (BMR + TDEE), weight loss/gain targets, macro breakdown.
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Calorie Deficit Calculator
Pick a daily calorie deficit, enter your current and goal weight, and see how many weeks it takes and the date you'd hit your target — with a safety check, browser-only
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Calories Burned Calculator
MET-based calorie burn for 30+ activities — running, cycling, swimming, HIIT, housework — stack and total — browser-only
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Cat Breed Finder (10-Question Lifestyle Quiz)
Cat breed finder — answer 10 lifestyle questions, get 5 matching cat breeds with personality, grooming needs, friendliness.
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Centripetal Force Calculator
Solve F = m·v²/r for force, mass, speed or radius, with angular speed ω and centripetal acceleration, browser-only
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Chemistry Equation Balancer
Chemistry equation balancer — paste an unbalanced equation, solve coefficients using the matrix method, show step-by-step.
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Chengyu Chain Game
Chengyu chain game with a 30,000+ idiom dictionary (full 汉语成语大词典 coverage). Start with any idiom; the computer continues with one whose first character matches your last.
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Chinese Idiom Search
800+ everyday chengyu — pinyin, origin, usage.
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Chinese Name Generator
Chinese name generator — meaningful Chinese names with pinyin, meaning, and stroke count.
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Chinese Numeric Converter
Arabic ⇄ Chinese number — simple (一二三), formal (壹貳參), or amount (金额大写 with 元角分).
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Chinese Pinyin Converter
Chinese characters to pinyin — with tone marks or numbers, supports simplified and traditional.
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Chinese Poetry Search
Chinese classical poetry — 300+ hand-annotated Tang/Song/Yuan canon (唐诗宋词元曲) plus 80,000+ searchable Tang/Song/Shijing/Chuci poems on demand.
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Chinese Stroke Counter
Chinese character stroke counter — count strokes for any hanzi, traditional or simplified.
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Chinese Zodiac Sign Checker (Sheng Xiao)
Chinese zodiac checker — your animal sign, element, compatibility, lucky numbers/colors by birth year.
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Chinese Zodiac Fortune (Daily / Monthly / Yearly)
Chinese zodiac fortune — daily/monthly/yearly outlook for 12 zodiac signs in love, career, wealth, health.
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Circle Calculator
Know any one of radius, diameter, circumference or area, get the other three, plus arc length and sector area, browser-only
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Classroom Color Wheel
Interactive color wheel with harmony explorer and color mixing — complementary, analogous, triadic, split-complementary, and tetradic schemes for teachers and students.
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Collatz Conjecture Calculator
Enter any positive integer, watch 3n+1 run to 1 — full hailstone sequence, stopping time, and peak, exact via BigInt
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College Major Matcher (Holland RIASEC, 40 Questions)
College major matcher — Holland code (RIASEC) test, 40 questions, recommend 10+ matching majors with career path.
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Color Mixer
Color mixer — blend any two colors with adjustable ratio, RGB/HSL/LAB color space, predict the result and copy hex.
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Columnar Transposition Cipher
Keyword sets the column order, the grid does the scrambling — encrypt, decrypt, regular or irregular padding, all in your browser
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Permutation & Combination Calculator
nPr, nCr, n!, n^r and combinations-with-repetition — exact BigInt results with the formula and worked steps — browser-only
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Combined Gas Law Calculator
P1V1/T1 = P2V2/T2 solver, find any one of the six gas quantities, with Boyle, Charles and Gay-Lussac special cases, browser-only
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Completing the Square Calculator
Turn ax² + bx + c into vertex form a(x − h)² + k with every step shown — vertex, axis of symmetry, min/max, and solved by completing the square — browser-only
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Complex Number Calculator
Complex number calculator — +-×÷ + conjugate + modulus + argument + polar/Cartesian conversion + powers + roots + Euler form, complex plane visualization.
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Compound Interest Calculator
Compound interest calculator — see how money grows over time, with monthly contributions, charts, and breakdown.
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Cone Calculator
Radius + height of a right circular cone, instant volume ⅓πr²h, slant height, lateral and total surface area, plus reverse-solve, browser-only
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Confidence Interval Calculator
Mean and proportion confidence intervals with margin of error, exact z critical values, one-click copy, browser-only
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Western Zodiac Calculator (Sun Sign)
Western zodiac calculator — your sign, element, ruling planet, compatibility, daily traits.
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Continued Fraction Calculator
Expand a decimal or fraction into a continued fraction [a0;a1,a2,...] with the convergents that best approximate it — browser-only
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Cooking Unit Converter
Cooking unit converter — tsp / tbsp / cup / oz / ml / g for 100+ common ingredients with density.
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Coordinate Distance Calculator
Great-circle distance between two lat/long points with the Haversine formula, plus bearing and midpoint, all in your browser
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Correlation Coefficient Calculator
Paste X,Y pairs → Pearson r, r², covariance, regression line and a scatter plot — runs entirely in your browser
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Coulomb's Law Calculator
F = k·q1·q2 / r² — solve electrostatic force, distance or charge, signed result, µC/nC units, scientific notation — browser-only
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Countdown Timer
Countdown timer — to any date and event, with live ticking down to seconds.
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Cover Letter Generator
Cover letter generator — fill 6 fields, pick a tone, get a tailored cover letter in 4 templates, bilingual.
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CSS Flexbox Generator
Generate production-ready flexbox CSS from visual controls — pick a layout preset, tweak properties, copy CSS, Tailwind, or React inline styles in one click.
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CSS Flexbox Playground
Visual CSS Flexbox sandbox — tweak container and item properties live, see the layout update instantly, copy ready-to-use CSS.
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CSV to LaTeX Table
Paste CSV, get a compile-ready LaTeX tabular with booktabs, l/c/r alignment, a table environment and safe escaping, all in your browser
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CSV Transposer
Flip CSV rows and columns from uploaded files or pasted data, with ragged-row handling and local output.
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Cylinder Calculator
Volume, surface area and capacity of a cylinder from radius or diameter and height — reverse-solve for height, see litres of water — browser-only
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Date Difference Calculator
Days / weeks / months / years between two dates — plus business-days mode — browser-only
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Day of the Week Calculator
Type any date and read the weekday back — works for 1066, 1900 or 3000, with day-of-year, ISO week and days-from-today
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Days Until Date Calculator
How many days until a date — plus weeks, months, business days, exact remaining, and the weekday it lands on
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Decibel Calculator
Add sound levels, convert ratio ⇄ dB (power 10·log, amplitude 20·log), and read a common-sound reference table — browser-only
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Decimal to Fraction Converter
Turn 0.75 into 3/4, type 0.(3) to get 1/3, or flip a fraction back to its decimal with the repeating block marked
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Density Calculator
Solve ρ = m / V for density, mass, or volume · mixed units (g, kg, lb, mL, L, cm³, gallon) · 20 substance presets · floats-or-sinks verdict — all browser-only
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Derangement Calculator
Subfactorial !n — the number of permutations where nothing stays in its own place, exact via BigInt, with the 1/e probability — browser-only
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Derivative Calculator (Step-by-Step)
Derivative calculator with step-by-step — symbolic differentiation, chain/product/quotient rule shown, plot f(x) and f'(x).
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Dew Point Calculator
Air temperature + relative humidity to the exact dew point, with a comfort band — Magnus formula, reversible, browser-only
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Dice Probability Calculator
Exact odds for any NdS roll: full sum distribution, expected value, and P(sum = / ≥ / ≤ X), counted not simulated
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Dilution Calculator
Solve C1V1 = C2V2 and ratio dilutions (1:10) — stock + water amounts in mL / L / fl oz / gal — browser-only
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Divisors Calculator
List every factor of a number — divisor count, sum of divisors, factor pairs, prime and perfect-number check — runs in your browser
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DNA to RNA Converter
Transcribe DNA to mRNA, build the reverse complement, translate codons to protein — standard genetic code, browser-only
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Dog Breed Finder (10-Question Lifestyle Quiz)
Dog breed finder — answer 10 questions about your lifestyle, get 5 matching breeds with size, temperament, exercise needs.
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DOI Deduplicator
Find duplicates and keep one clean copy of dois from pasted text or uploaded local files.
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DOI Extractor
Extract, dedupe, and export dois from pasted text or uploaded local files.
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DOI List Converter
Convert dois from pasted text or uploaded local files.
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DOI List Validator
Validate and explain issues in dois from pasted text or uploaded local files.
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DOI Normalizer
Normalize, sort, and prepare dois from pasted text or uploaded local files.
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Double Factorial Calculator
Exact n!! computed on BigInt — the full expansion (7!! = 7×5×3×1 = 105), odd or even chain, and the bridge to the ordinary factorial, all in your browser
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Dream Interpretation Dictionary (Zhougong + Jung)
Dream dictionary — search dream symbols and meanings (Chinese 周公解梦 + Jungian).
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Dutch 500 Essential Words
Dutch 500 essential A1–A2 words — IPA + de/het articles + 6-person conjugation + audio TTS.
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Egyptian Fraction Calculator
Turn any proper fraction into a sum of distinct unit fractions with the Fibonacci-Sylvester greedy algorithm, with the steps shown, browser-only
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Electricity Cost Calculator
Power × hours × tariff → kWh and cost per day, month, and year — add multiple appliances, account for standby — browser-only.
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Emoji Finder
Unicode 15.1 / 1500+ emojis with bilingual search — one-click copy, browser-only
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Engineering Notation Converter
Plain number ⇄ engineering notation (×10³ⁿ) ⇄ SI prefix (47kΩ) — exponent always a multiple of 3, with scientific notation for contrast — browser-only
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English Collocations
English collocations reference — 200+ common verb + noun / adj + noun / verb + prep collocations with usage examples.
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English Grammar Rules Reference
English grammar rules reference — 60+ core grammar rules with side-by-side examples, common mistakes, bilingual explanations.
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English Irregular Verbs Reference
English irregular verbs reference — 200+ verbs with base / past / past participle, Chinese gloss, in-browser audio, pattern filter, and a flash-card practice mode.
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English Vocabulary Test
English vocabulary test — estimate your vocab size in 5 minutes, levels CET-4 / CET-6 / IELTS / TOEFL / GRE.
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Escape Velocity Calculator
v = √(2GM/r) — escape + orbital velocity for any planet, moon or star, in m/s, km/s and mph — browser-only
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Expected Value Calculator
E[X] = Σ x·p — enter outcomes and probabilities, get expected value, variance and standard deviation, all in your browser
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Expense Tracker
Expense tracker — log spend, categorize, see monthly totals, all in your browser.
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Factorial Calculator
Exact n! for any non-negative integer, with digit count, trailing zeros, double factorial and scientific notation, computed on BigInt right in your browser
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Fibonacci Generator
First N terms, a range, or the nth value, with running sum and golden-ratio convergence, exact via BigInt, all in your browser
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Final Grade Calculator
Current grade + final weight + target → exactly what you need on the final — browser-only
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Fish Tank Calculator
Fish tank size calculator — input fish species and count, get the minimum tank gallons/liters needed and stocking density warnings.
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Fraction Calculator
Add, subtract, multiply, divide fractions — auto-reduced, with steps, mixed ⇄ improper ⇄ decimal — browser-only
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Free Fall Calculator
h = ½gt² · v = √(2gh) · solve from height, time, or impact speed · Earth, Moon, Mars gravity · browser-only
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French 1086 Essential Words — DELF A1, A2, B1, B2 & Professions
1086 French entries — 1036 DELF A1-B2 core words plus 50 profession words. IPA, gender, Bescherelle conjugation (présent / passé composé / futur simple), free TTS, 17 categories.
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Frequency Wavelength Calculator
Convert frequency to wavelength and back with λ = v/f, pick the wave speed, read the EM spectrum band, copy in one click, browser-only
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Frustum Volume Calculator
Conical frustum (truncated cone) volume, slant height, lateral and total surface area from R1, R2 and h — browser-only, one-click copy
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Fuel Cost Calculator
Trip fuel cost from distance + economy + price — round trip, per-person split, L/100km ⇄ MPG — browser-only.
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Future Value Calculator
Project the future value of a lump sum plus regular contributions — full time-value-of-money math, year-by-year, browser-only
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2048 Game (Slide, Merge, Reach 2048)
2048 game — slide tiles, combine numbers, reach 2048. Pure browser, no ads, your high score saved locally.
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GC Content Calculator
Paste a DNA or RNA sequence and get GC%, AT%, per-base counts, length and a melting-temperature estimate. FASTA headers and spaces are ignored, invalid bases flagged, all in your browser.
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GCD & LCM Calculator
GCD + LCM of any list of integers — Euclidean steps, prime factorization, prime-factor table — exact BigInt math, browser-only
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Gear Ratio Calculator
Gear & transmission ratio plus bicycle gear inches, development and speed from cadence — exact, browser-only
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Geometric Sequence Calculator
Geometric sequence calculator — nth term, sum of first n terms, and infinite series sum from first term a and common ratio r, all in your browser.
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German 500 Essential Words
German 500 essential words (A1-A2 + B1 core) with IPA, der/die/das, full Präsens, Präteritum, Perfekt, Partizip II for verbs, and browser TTS.
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GPA Calculator
Weighted GPA from courses + credits + grades — US 4.0 / 4.3 and China 4.0 / 4.5 conversion, letter ⇄ percentage ⇄ point — browser-only
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Grade Calculator
Weighted course grade + what you need on the final — multi-row categories, letter grade, shareable link — browser-only
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Graph Paper Generator
Printable square, dot, isometric, ruled and coordinate paper as crisp SVG sized in real millimetres, runs entirely in your browser
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Gravitational Force Calculator
F = G·m1·m2 / r² · solve for force, distance or mass · scientific notation · Earth/Moon/Sun presets · 100% browser-only
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Gray Code Converter
Decimal, binary and Gray code three ways, gray = n^(n>>1), one click each side, all in your browser
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Half-Life Calculator
Solve any radioactive-decay unknown — initial amount, remaining amount, elapsed time, or half-life — with exact exponential math, all in your browser
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Hamming Code Calculator
Encode, decode and error-correct Hamming (SEC / SECDED) codes — syndrome, parity coverage, one-click copy — browser-only
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Hamming Distance Calculator
Count the differing positions between two equal-length inputs, in characters, binary bits or integer XOR, all in your browser
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Handwriting Practice Sheet
Handwriting practice sheet generator — Chinese 米字格 / 田字格 / 四线三格 (English) PDF-ready printable.
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Happy Number Checker
Replace N with the sum of its squared digits — reach 1 and it is happy, hit the 4-cycle and it is not. See every step.
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Heart Rate Zones Calculator
Heart rate zones calculator — max HR (4 formulas) + 5 training zones (recovery/aerobic/tempo/threshold/VO2max), with workout examples.
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Heat Index Calculator
Air temperature + humidity to the real "feels-like" temperature, with NWS risk level — exact Rothfusz regression, browser-only
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Henderson-Hasselbalch Calculator
Buffer pH = pKa + log([A⁻]/[HA]) — forward and reverse, acetate/phosphate/Tris/bicarbonate presets — browser-only
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Hindi 1300 Essential Words
Hindi 1300 essential A1–A2 words — Devanagari, IAST, IPA, gender, -nā verbs, audio TTS.
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Hooke's Law Calculator
F = k·x spring calculator: solve any one of force, spring constant or displacement from the other two, plus elastic potential energy ½kx² — browser-only
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HSK Chinese Vocabulary Test
HSK Chinese vocabulary test — estimate your Mandarin level (HSK 1-6) in 5 minutes with real exam words.
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ID Photo Resizer
Resize any photo to passport, visa, or ID spec — center-crop to exact pixels, fully in-browser, no upload
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Ideal Gas Law Calculator
Solve PV = nRT for pressure, volume, amount, or temperature — pick any unknown, mix any units, runs in your browser
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Ideal Weight Calculator
Devine + Robinson + Miller + Hamwi formulas, side by side, plus the healthy BMI weight band — metric and imperial — browser-only
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IEEE 754 Floating Point Converter
Decimal to single and double precision bits, sign exponent mantissa split, full hex and binary, all in your browser
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IELTS Band Calculator
IELTS band calculator — convert listening/reading raw scores to band, average four skills, see your overall band.
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Indonesian 500 Essential Words
Indonesian 500 essential A1–A2 words — KBBI spelling + Jakarta IPA + audio TTS. No tones, no conjugation.
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Integral Calculator (Step-by-Step)
Indefinite integral calculator step-by-step — symbolic integration, substitution + integration by parts shown, plot f(x) and F(x).
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Intermittent Fasting Tracker — 16:8 / OMAD / 5:2 / 36h Timer with Stages
Intermittent fasting tracker — 16:8 / 18:6 / 20:4 / OMAD / 5:2 / 36h timer with stages and history log.
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Interview Questions Bank
Interview questions bank — 300+ real questions across behavioral / technical / case / culture, with strong answer frameworks.
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ISSN Validator
Check an 8-digit journal ISSN with the MOD 11 check digit — single or batch, computes the check character, one-click copy, browser-only
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Italian 500 Essential Words
Italian 500 essential words (A1-A2 Plida) with IPA, gender, full verb conjugation, audio TTS.
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Japanese 500 Essential Words (JLPT N5 + N4)
Japanese 500 essential words covering JLPT N5 and N4, with kana, romaji, kanji and audio TTS.
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Jet Lag Calculator
Estimate how many days jet lag will last and build a day-by-day plan to pre-shift your body clock before you fly — eastbound vs westbound, light and melatonin timing, all in your browser
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Julian Date Converter
Gregorian date ⇄ Julian Day Number (JDN), fractional JD, Modified Julian Date (MJD) and ordinal day-of-year — astronomy-grade, browser-only
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Kanji & Chinese Character Stroke Order Viewer
Kanji + Chinese character stroke order viewer — animated SVG showing correct stroke sequence + direction, with romaji/pinyin/meaning, 500+ common characters.
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Kids Allowance Calculator
Kids allowance calculator — age-appropriate weekly/monthly amount with chore-based breakdown, savings goal sandbox.
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Kinetic Energy Calculator
KE = ½mv², solve for energy, mass or speed, with formula steps and momentum, all in your browser
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Korean 500 Essential Words (TOPIK I–II)
Korean 500 essential words spanning TOPIK I and TOPIK II — start speaking Korean today with Hangul, romanization, audio TTS, and full verb conjugations.
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LaTeX Equation Editor (Live Preview)
LaTeX equation editor live — type/paste LaTeX, see math rendered live via MathJax 3 (CDN), copy as SVG/PNG/Markdown/MathML, 30+ symbol palette.
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Lean Body Mass Calculator
Boer, James and Hume LBM side by side, plus fat mass and a direct body-fat path, metric or imperial, fully in your browser
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Leap Year Checker
Is it a leap year? Type any year for a yes/no, the 4/100/400 rule worked out, Feb length, and the next leap year, browser-only
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Lens Equation Calculator
Solve 1/f = 1/do + 1/di — enter any two of focal length, object and image distance, get the third plus magnification and a real/virtual verdict, browser-only
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Light Year Converter
Type one distance, read it as light-years, parsecs, AU, light-seconds, km and miles at once, all in your browser
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Logarithm Calculator
log_b(x), ln, log₁₀, log₂ and antilog in one place — change-of-base steps shown, one-click copy, browser-only
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Lunar Calendar Converter (Chinese Nongli)
Gregorian ⇄ Chinese Lunar (Nongli) calendar — bi-directional, accurate 1900-2100.
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Macro Nutrient Calculator
Macro nutrient calculator — TDEE + protein/fat/carb split for cut/maintain/bulk goals, with 3 split presets (high-protein/keto/balanced) and meal example.
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Marathon Time Predictor
Marathon time predictor — input 5k/10k/half time, get full marathon prediction via 3 formulas (Riegel/Cameron/VDOT), with pace zones and weekly mileage advice.
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Markdown Cheat Sheet
Markdown syntax cheat sheet — every rule with live preview side by side, GFM + flavors.
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Markdown Link Extractor
Upload Markdown and extract inline links, reference links, images, and bare URLs into a local CSV.
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Math Formula Reference
Math formula reference — algebra, geometry, trigonometry, calculus, statistics, all in one place.
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Matrix Calculator
Matrix calculator — add/sub/multiply/inverse/determinant/transpose/rank/RREF/eigenvalues for n×m matrices, step-by-step.
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MBTI Quick Test (28 Questions, 16 Personality Types)
MBTI quick test — 28 questions, 5 minutes, get your 4-letter type with detailed reading.
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Online Metronome
Rock-steady practice metronome — tap tempo, time signatures, accented downbeat, subdivisions. Web Audio, nothing recorded, nothing uploaded.
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Modular Exponentiation Calculator
Compute a^b mod m with fast exponentiation and BigInt, plus modular inverse and step-by-step squaring, all in your browser
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Modulo Calculator
a mod n in both conventions — the % your language returns AND the math mod that is never negative, plus floor quotient, modular power and inverse
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Molality Calculator
Molal concentration b = n / m — moles of solute per kilogram of solvent, solve any one of moles, solvent mass, or molality, or start from grams + molar mass, browser-only
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Molar Mass Calculator
Type any chemical formula — get molar mass, a per-element mass-percent table, and mass↔mole conversion. IUPAC weights, browser-only.
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Molarity Calculator
Molar concentration c = n / V — solve any one of moles, volume, concentration, or go straight from grams + molar mass — browser-only
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Moment of Inertia Calculator
Pick a shape, enter mass and size, read I in kg·m² — cylinder, sphere, rod, point mass, plus rotational KE — browser-only
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Momentum & Impulse Calculator
p = m·v and J = F·Δt = Δp — solve any one of momentum, mass, velocity, impulse, force or time, with kg·m/s, g, m/s and km/h units — browser-only
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Moon Phase Calculator
Pick any date, see the moon phase, illumination percentage and moon age, plus this month's principal phases, all in your browser
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Morse Code Translator
Text to Morse code and back — encode, decode, audio playback, ITU standard.
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Multinomial Coefficient Calculator
n! / (k1!·k2!·…) computed exactly with BigInt — ways to split n items into fixed-size groups, the multinomial-theorem term coefficient, browser-only
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Multiplication Table Generator
Single times table, full N×N grid, or the Chinese 99 chant — copy, print, share
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NATO Phonetic Alphabet Converter
Text to Alpha Bravo Charlie and back — spell anything aloud over the phone or radio, no mishearing.
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Number to Words
Spell any number in English — cheque amounts, ordinals, British vs American "and" — 100% browser-only
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Ohm's Law Calculator
Enter any two of voltage, current, resistance, or power — get the other two plus the formula used — with mV/V/kV, µA/mA/A, Ω/kΩ/MΩ, mW/W/kW prefixes — browser-only.
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One-Rep Max Calculator
Estimate your 1RM from any set with five formulas at once, then read a full %1RM training-load table — kg or lb, browser-only
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Orbital Period Calculator
T = 2π·√(a³ / GM) · Kepler's third law · solve period or semi-major axis · orbital speed · Sun/Earth/Jupiter presets · 100% browser-only
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ORCID Validator
Check an ORCID iD check digit with ISO 7064 MOD 11-2, complete the check digit from the first 15 digits, validate a whole list, all in your browser
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Ordinal Number Converter
Cardinal to ordinal both ways: 1st 2nd 3rd suffixes, twenty-first words, plus Chinese 第N, single or batch, copy ready
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Ovulation & Fertility Tracker
Ovulation & fertility tracker — predict next 6 months of fertile windows, track BBT, find best conception days.
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Palindrome Checker
Tells you if text reads the same backwards, finds the longest palindrome inside, handles Chinese and emoji, runs in your browser
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Palmistry Guide — 6 Major Lines & 7 Mounts with Diagrams
Palmistry guide — 6 major lines + 7 mounts explained with diagrams, traditional readings, bilingual.
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Pascal's Triangle Generator
Generate any number of rows, read off every binomial coefficient C(n,k), highlight one row as a binomial expansion, copy or share — runs fully in your browser
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Password Strength Checker
Check password strength — entropy, time-to-crack, breach pattern check (offline).
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Pendulum Period Calculator
T = 2π√(L/g) — solve a simple pendulum's period, frequency or length, with Earth, Moon and Mars gravity, browser-only
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Percent Composition Calculator
Mass percent of every element in a compound — type a formula, read the breakdown — IUPAC atomic weights, browser-only
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Percent Error Calculator
Compare a measured value against the true value — get percent error, absolute error, relative error, and signed high/low. Plus a percent-difference mode for two trials with no accepted answer.
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Percent to Fraction Converter
Percent ⇄ fraction, both ways. 25% becomes 1/4, 3/4 becomes 75%, decimal percents and values over 100% included, fully reduced, browser-only.
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Percent Yield Calculator
actual ÷ theoretical × 100 — solve for percent, actual or theoretical yield, grams or moles, with a plain-English read on why it is below or above 100% — browser-only
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Percentage Calculator
5 common percentage calculations — "x% of y", "x is what% of y", percentage change, increase/decrease — instant, browser-only
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Percentage Change Calculator
Growth rate, drop, percentage-point gap, and reverse-solve the new value — signed, color-coded, browser-only
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Percentile Calculator
Any percentile P plus Q1 Q2 Q3, IQR, five-number summary, box plot and 1.5×IQR outliers, browser-only
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Periodic Table
Interactive periodic table — 118 elements, properties, electron config, search.
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Pet Age Calculator
Pet age calculator — accurate dog/cat human-age equivalent, with breed size adjustment, lifespan stages.
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Pet Food Calculator
Pet food calculator — RER + activity factor for dogs and cats, exact daily grams based on weight, age, neuter status, and kibble kcal/100g.
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pH Calculator
pH, pOH, [H+] and [OH-] from any one value, with an acid/base verdict and a 0-14 colour scale, all in your browser
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Photon Energy Calculator
Wavelength or frequency in, photon energy out in joules and eV — Planck equation E = hf = hc/λ, with EM band — browser-only
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Piano Chord Finder
Piano chord finder — type any chord (Cmaj7, F#m, Bdim) and see the keys highlighted on a piano, with notes and inversions.
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Barbell Plate Calculator
Target weight → exactly which plates to slide on each end — kg & lb, with a live barbell diagram — browser-only
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Playfair Cipher Encoder & Decoder
Encrypt and decrypt with a 5x5 keyword square, digraph pairs and a live grid, browser-only
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Polar / Rectangular Coordinate Converter
Convert (x, y) to (r, θ) and back, degrees or radians, with a live coordinate diagram, browser-only
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Polybius Square Cipher Encoder & Decoder
Turn letters into 5x5 grid coordinates and back, with a keyword square, origin switch and a live grid, browser-only
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Pomodoro Timer
Pomodoro timer — 25/5 classic, plus 50/10 and 90/15 long-focus modes, with sound, browser tab title, daily stats.
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Pool Volume Calculator
Find how many gallons (and liters and cubic meters) your pool holds — rectangle, round, oval, or sloped floor — in feet or meters
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Portuguese 500 Essential Words
Portuguese 500 essential words — A1 to A2 Brazilian Portuguese, with IPA, gender, conjugation, audio TTS.
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Pregnancy Weight Gain Calculator
Pre-pregnancy BMI + week → IOM recommended total gain, the by-week target, and an on-track check — singleton & twins — browser-only
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Prime Factorization Calculator
Break any integer into prime factors with exponent form, divisor count and full divisor list, exact BigInt math, browser-only
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Prime Number Calculator
Test primality · factorize · list primes in a range · find the N-th prime — exact BigInt math, browser-only
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Probability Distribution Visualizer
Probability distribution visualizer — normal/t/chi-sq/F/binomial/poisson/exp/uniform PDF+CDF, P(a≤X≤b) area, z/p table replacement.
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Projectile Motion Calculator
Solve flight time, max height, range & impact speed from launch speed, angle and height — with a live trajectory plot, browser-only
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Prompt Template Library
200+ prompt templates for ChatGPT, Claude, Gemini — copy-paste, browse by use case.
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Protein Intake Calculator
Protein intake calculator — daily grams by body weight, activity, goal (cut/maintain/bulk), per ISSN 2017 guidelines.
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Punnett Square Calculator
Cross two genotypes — Aa × Aa or AaBb × AaBb — get the grid, the genotype ratio and the phenotype ratio, one-click copy, browser-only
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Pythagorean Theorem Calculator
Solve a²+b²=c² — find the hypotenuse, find a missing leg, or measure the distance between two points (2D & 3D). Browser-only.
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Python Cheatsheet
Python cheat sheet — 100+ idiomatic Python snippets for string, list, dict, file, async, with real examples.
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Quadratic Equation Solver
Quadratic equation solver — ax² + bx + c = 0, discriminant analysis, real + complex roots, vertex/intercepts, parabola visualization.
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Rail Fence Cipher Encoder & Decoder
Encrypt, decrypt and brute-force a rail fence zigzag cipher, with a live grid, rail count plus offset, browser-only
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Random Number Generator
Generate cryptographically-secure random integers — single or batch, with/without duplicates — browser-only
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Ratio Calculator
Solve a:b = c:x, simplify ratios, split a total by a ratio, scale a recipe up or down — with full steps, browser-only
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Readability Score Checker
Paste English text and get Flesch Reading Ease plus five grade-level scores, syllable counts, and reading time — runs entirely in your browser
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Reading Time Calculator
Paste text, get an accurate "X min read" plus a separate speaking time — counts CJK by character and English by word, all in your browser
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Recipe Scaler
Recipe scaler — paste any recipe, change servings, get all ingredient amounts auto-scaled. Handles fractions and unit conversion.
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Regex Cheatsheet
Interactive regex cheat sheet — quick reference for every flavor (JS, Python, PCRE).
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Regular Polygon Calculator
Sides n + side length s, get area, interior angle, apothem and both radii, with a to-scale n-gon drawn live, browser-only
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Resistor Color Code Calculator
Decode 4, 5 and 6-band resistors to Ω, tolerance and tempco — or go the other way, with a live color-band drawing
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Rocket Equation Delta-v Calculator
Tsiolkovsky Δv = ve·ln(m0/mf) — solve from exhaust velocity or specific impulse, reverse-solve propellant, mass ratio, browser-only
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Roman Numeral Converter
Arabic ⇄ Roman, both directions, live — strict validation, step-by-step breakdown, vinculum up to 3,999,999 — 100% browser-only
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Roman Numeral Date Converter
Turn any date into Roman numerals for tattoos, wedding bands, copyright years and cornerstones, then read them back the other way, all in your browser
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ROT13 Encoder & Decoder
ROT13 / ROT47 / Caesar cipher — encode and decode in your browser, instant.
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ROT47 Encoder & Decoder
Rotate all visible ASCII by 47. Digits and symbols change too, fully self-inverse, runs in your browser.
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Rule of 72 Calculator
Estimate doubling time from a rate (72 ÷ r), or the rate from a target time — side by side with the exact ln(2)/ln(1+r) figure — browser-only
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Running Pace Calculator
Running pace calculator — convert between pace / time / distance, predict 5K/10K/half/full marathon from one race.
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Russian 500 Essential Words (TORFL A1-A2)
Russian 500 essential words covering the full TORFL A1-A2 syllabus, with Cyrillic, stress marks, BGN/PCGN romanization, gender, full verb conjugation, and audio TTS.
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Safe Period & Ovulation Calculator
Period & ovulation calculator — predict next period, fertile window, safe days (based on calendar method).
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Sample Size Calculator
How many people to survey for a given confidence and margin of error — finite-population correction, reverse mode, one-click copy, browser-only
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Savings Goal Tracker
Savings goal tracker — set a target (down payment, trip, emergency fund), see weekly/monthly contribution and projected date.
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Schwarzschild Radius Calculator
R_s = 2GM/c² — turn any mass into its black-hole event horizon, in metres, km or light-seconds, with presets and inverse solve — browser-only
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Scientific Calculator
Scientific calculator — sin / cos / log / sqrt / power, with full keyboard input + history, deg/rad mode.
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Scientific Notation Converter
Plain ⇄ scientific (a×10ⁿ) ⇄ engineering ⇄ E-notation — with significant figures, exact big/small numbers — browser-only
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Screen Time Budget
Screen time budget — track and visualize daily screen time across phone/tablet/PC, with age-based recommendations from WHO/AAP.
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Scytale Cipher Encoder & Decoder
Encrypt and decrypt the ancient Spartan scytale rod cipher, with a live rod grid and an adjustable diameter, browser-only
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Chinese Zodiac Compatibility (Shengxiao Match)
Chinese zodiac compatibility — match two people by their zodiac signs, 144 pair combinations with reading.
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Significant Figures Calculator
Count sig figs · round to N significant figures · do sig-fig arithmetic — exact string-level math, browser-only
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Simple Interest Calculator
I = P × r × t — solve for interest, principal, rate, or time, plus total and a simple-vs-compound gap — browser-only
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Simplify Fraction Calculator
Reduce any fraction to lowest terms, see the GCD it divided by, and flip between improper and mixed forms, all in your browser
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Sleep Cycle Calculator
Sleep cycle calculator — 90-minute REM cycles. Find best bedtime if you must wake at X, or best wake time if you sleep at Y.
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Sleep Debt Calculator
Sleep debt calculator — track this week's sleep hours, see your accumulated debt, get a realistic recovery plan based on research.
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Slope Calculator
Two points in, full line out — slope, angle, distance, midpoint, y = mx + b and grade % — browser-only
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Snell's Law Calculator
n1·sin(θ1) = n2·sin(θ2) — solve refraction angle, critical angle and total internal reflection — browser-only
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Spanish 500 Essential Words
Spanish 500 essential A1–A2 words — start speaking Spanish today, with pronunciation, example sentences, verb conjugations and audio TTS.
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Special Number Checker
Type one integer, see at a glance whether it is prime, perfect, abundant, deficient, triangular, square, cube, Fibonacci, palindrome, with the reason for each, browser-only
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Specific Heat Calculator
Q = m·c·ΔT — solve for any of heat, mass, specific heat or temperature change, with water/aluminum/iron/copper presets and J/kJ/cal units — browser-only
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Sphere Calculator
Type any one of radius, diameter, volume or surface area — the other three solve instantly, plus how many liters the ball holds — browser-only
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SQL Cheatsheet
SQL cheat sheet — 100+ statements covering SELECT, JOIN, window functions, indexing, MySQL/PostgreSQL/SQLite differences.
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Stair Climbing Calorie Calculator
Stair climbing calorie calculator — calculate kcal burned by floors climbed, with METs-based formula.
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Statistics Basic Calculator
Basic statistics calculator — mean/median/mode/variance/std-dev/quartiles/range/IQR/skewness/kurtosis + histogram + box plot, paste any numbers.
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Stefan-Boltzmann Law Calculator
P = εσAT⁴ — radiated power, radiant exitance and the inverse (power → temperature), with Sun and body presets — browser-only
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Strength 1RM & Training Program
Strength 1RM calculator + training program — 6 formulas (Epley/Brzycki/Lombardi/O'Conner/Lander/Mayhew), %1RM table, Wendler 5/3/1 + Sheiko + Madcow templates.
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Sudoku Generator
Sudoku generator and solver — 4 difficulties (easy / medium / hard / expert), unique-solution guaranteed, play in the browser or print as PDF.
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Superscript & Subscript Text Generator
Turn x2 into x², H2O into H₂O — real Unicode you can paste into Instagram, a spreadsheet or a video title, no rich text needed
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Tally Marks Converter
Number to tally marks and back, in Unicode, the five-bar gate, or Chinese 正, with one-click copy, all in your browser
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Tap Code Translator
Knock cipher on a 5×5 grid, C and K share a cell, row taps then column taps, decode back to text, all in your browser
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Tarot Reading (78-Card Rider-Waite-Smith Deck)
Tarot reading — full 78-card deck, 4 spreads (one-card / three-card / Celtic Cross / love), bilingual interpretations.
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TDEE Calculator
TDEE calculator — BMR × activity factor, with cut/bulk calorie targets and projected weekly weight change.
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Temperature Converter
One temperature in, all four scales out — Celsius, Fahrenheit, Kelvin, Rankine — live formula, reference points, browser-only
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Tempo Delay Calculator
Turn any BPM into a full delay-time table — milliseconds and Hz for every note value, plus dotted and triplet. Built for mixing and producing.
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Test Grade Calculator
Answers wrong → percent + letter grade + a full printable grading chart — the teacher's EZ Grader, browser-only
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Text File Cleaner
Upload a text file and remove BOM, null bytes, trailing spaces, and excessive final blank lines locally.
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Text File Line Ending Converter
Upload or paste text and convert CRLF, CR, and LF endings to a consistent LF or CRLF output locally.
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Text Sorter
Sort lines alphabetically, naturally (file2 < file10), numerically, by length — locale-aware — browser-only
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Text to Binary Converter
Text to binary (and back) — UTF-8 aware, 8/16/32 bit grouping, emoji safe.
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Text to Speech
Read any text aloud with your browser's built-in voices — pick voice, speed, pitch, volume — 100% local, nothing uploaded
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Thai 500 Essential Words
Thai 500 essential A1–A2 words — Thai script + RTGS + IPA + 5 tones + audio TTS.
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Timezone Converter
Convert any time between any two timezones — DST-aware, IANA database — browser-only
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Traditional ⇄ Simplified Chinese Converter
Traditional ⇄ Simplified Chinese — fast, character-level, no API.
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Triangle Calculator
Triangle solver — SSS, SAS, ASA, AAS, and the ambiguous SSA case via law of sines + law of cosines. All sides, angles, area, perimeter, type, drawn to scale.
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Trigonometry Calculator
Trigonometry calculator — sin/cos/tan + inverse + sec/csc/cot, degree/radian/gradient, unit circle visualization, exact values.
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Turkish 500 Essential Words
Turkish 500 essential A1–A2 words — Istanbul standard + IPA + vowel harmony + audio TTS.
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Two's Complement Converter
Signed decimal to two's complement binary and hex at 4, 8, 16, 32, 64 bits, with sign-magnitude and one's-complement steps, runs in your browser
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Typing Speed Test
Typing speed test — WPM, accuracy, real-time mistakes, English + Chinese pinyin modes.
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Unit Converter
Convert between length, weight, temperature, area, volume, speed, time — instant, browser-only
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Vector Calculator
Add, subtract, scale, dot, cross, magnitude, angle, unit vector and projection for 2D and 3D vectors — browser-only
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Vietnamese 500 Essential Words
Vietnamese 500 essential A1–A2 words — chữ Quốc ngữ + IPA + 6 tones + audio TTS.
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Vigenère Cipher Encoder / Decoder
Encrypt and decrypt with a keyword, polyalphabetic shift, case kept, non-letters passed through, browser-only
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VO₂max Calculator
Estimate your maximal oxygen uptake from four field tests — Cooper run, 1.5-mile, resting HR, Rockport walk — with a fitness grade by age and sex
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Waist-to-Height Ratio Calculator
WHtR = waist ÷ height, one number that flags abdominal fat better than BMI, with cm/in, sex-aware bands and one-click copy, browser-only
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Waist-to-Hip Ratio Calculator
WHR = waist ÷ hip, scored against the WHO health-risk bands by sex, with an optional waist-to-height check — runs entirely in your browser
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Water Intake Calculator
Water intake calculator — daily water target by body weight, activity, climate. With drink-log to track today's progress.
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Wavelength Frequency Calculator
Convert between wavelength λ, frequency f, and photon energy E · c = λf · E = hf · spectrum band + visible colour · browser-only
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Weight Loss Tracker & Calorie Deficit Calculator
Weight loss tracker — set target, log daily weight, see trend, project goal date with real calorie math.
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Weight Training Tracker — 1RM Calculator & Strength Progress Log
Weight training tracker — log compound lifts (squat/bench/deadlift/OHP), track 1RM via Epley formula, see strength gains by week.
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Weighted Average Calculator
Any value × weight pairs, weighted mean = Σ(value×weight)/Σweight, plus plain average and per-row contribution, browser-only
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Weighted Grade Calculator
Items + weights → your current course grade, with letter and banked points — browser-only
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Wind Chill Calculator
Turn air temperature and wind speed into a feels-like number — and a frostbite warning — using the official NWS / Environment Canada formula. Metric or imperial, browser-only.
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Word Counter
Count words, characters, sentences, paragraphs and reading time in any text — instant, browser-only
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Words to Number Converter
Type a number in English or Chinese words, get the digits back — one hundred twenty-three → 123, 一万两千三百 → 12300 — browser-only
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Work and Power Calculator
W = F·d·cosθ and P = W/t — solve work, power or force, with angle, P = F·v and HP ⇄ W — browser-only
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Wuxing Name Recommender (Five Elements Naming)
Five Elements (Wuxing) name recommender — based on Bazi gaps, suggest characters that balance the missing elements.
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Yoga Pose Library
Yoga pose library — 60+ asanas with Sanskrit + Chinese + English names, benefits, contraindications, modifications.
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Z-Score Calculator
Standardize any value, reverse a z-score back to raw, or compute μ and σ from a dataset — with left/right/two-tailed normal probabilities and percentile
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Zhuyin (Bopomofo) Converter
Hanyu Pinyin to Zhuyin ㄅㄆㄇㄈ both ways, tone marks ˊˇˋ˙, batch by space, copy in one click, runs in your browser