Calculator for Developer
28 calculator tools hand-picked for Developer.
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Age Difference Calculator
The exact gap between two birthdays — years/months/days, percentage, and the date one person is twice the other's age — browser-only
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AI Token Counter
AI token counter — estimate token count for GPT / Claude / Gemini, with per-model cost calculator (2026 pricing).
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Aspect Ratio Calculator
Calculate aspect ratio — fix any 1 of [width, height, ratio], get the other two.
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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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Business Days Calculator
Working days between two dates, or a date N working days out — weekends + holidays excluded, browser-only
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Duration Converter
Seconds ⇄ minutes ⇄ hours ⇄ days ⇄ weeks, plus human-readable, ISO 8601 duration and HH:MM:SS — one input, every format — browser-only
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ISO Date Deduplicator
Find duplicates and keep one clean copy of iso dates from pasted text or uploaded local files.
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ISO Date Extractor
Extract, dedupe, and export iso dates from pasted text or uploaded local files.
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ISO Date List Converter
Convert iso dates from pasted text or uploaded local files.
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ISO Date List Validator
Validate and explain issues in iso dates from pasted text or uploaded local files.
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ISO Date Normalizer
Normalize, sort, and prepare iso dates from pasted text or uploaded local files.
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Linux Permission (chmod) Calculator
Linux permission (chmod) calculator — convert between octal (755), symbolic (rwxr-xr-x), and ls -l forms, with safety warnings.
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LLM Pricing Calculator
Estimate daily and monthly LLM spend from tokens, request volume, and editable model prices.
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Meeting Cost Calculator
Meeting cost calculator — see how much that meeting is costing in real-time, with team salary data and overhead multiplier.
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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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Number Formatter
One number in, every format out: thousands grouping, currency, percent, scientific, engineering, compact (K/M/万), ordinal, byte size — plus reverse parsing. 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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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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PPI Calculator
Pixel density, dot pitch, physical size, aspect ratio & a retina check from resolution + diagonal — all in your browser
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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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PX REM EM Converter
CSS px ↔ rem ↔ em converter — visual scale, base font size adjustable.
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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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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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Unix Timestamp Converter
Unix timestamp ⇄ human date — seconds / milliseconds / ISO 8601 — UTC and local — browser-only
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Timezone Meeting Planner
Plan meetings across timezones — see when everyone's working hours overlap.
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Typing Speed Test
Typing speed test — WPM, accuracy, real-time mistakes, English + Chinese pinyin modes.
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Week Number Calculator
What week number is today? ISO 8601 (Mon-start) + US (Sun-start), plus year + week → date range — browser-only