What is a musical interval?

An interval is the pitch distance between two notes, measured in semitones (half steps). From C to G is seven semitones, which music theory names a Perfect 5th. The calculator gives you both numbers at once: the count of semitones and the conventional name, so you can move between the math and the theory without a chart.

Why is C to G a perfect fifth of 7 semitones?

Count up the chromatic scale from C: C#, D, D#, E, F, F#, G. That is seven half steps, and seven semitones is the definition of a Perfect 5th in twelve-tone equal temperament. Its just-intonation frequency ratio is close to 3:2, which is why the fifth sounds so stable and is the basis of power chords.

What is the difference between a major third and a minor third?

A major 3rd spans four semitones (C to E) and sounds bright; a minor 3rd spans three (C to Eb) and sounds darker. Stacking a major 3rd then a minor 3rd builds a major chord, the reverse builds a minor chord. The tool labels each so you do not have to recount half steps every time.

What are cents and why does the tool show them?

A cent is one hundredth of a semitone, so an equal-tempered semitone is exactly 100 cents and an octave is 1200. Cents let you compare interval sizes precisely, which matters when you tune or compare equal temperament against just intonation. A Perfect 5th reads 700 cents here, slightly narrower than the pure 3:2 ratio of about 702 cents.

How do sharps and flats work in the input?

Write the accidental right after the letter and before the octave, like C#4 or Bb3. The parser treats enharmonic spellings as the same pitch, so C#4 and Db4 both land on the same key. Results spell black keys with sharps (C#, F#), which keeps the output consistent no matter how you typed the input.

How many semitones are in an octave?

Twelve. An octave doubles the frequency, a 2:1 ratio, and twelve-tone equal temperament splits that doubling into twelve equal semitones of 100 cents each. So C4 to C5 is 12 semitones and 1200 cents. Intervals wider than an octave are compound; the tool folds them to a simple interval plus the number of octaves.

Name an interval while transcribing by ear

You hear a leap in a melody and want to label it. Drop the two notes in, say A3 and E4, and the tool tells you it is a Perfect 5th, seven semitones. No counting half steps on a keyboard diagram or second-guessing whether that gap was a fourth or a fifth. The name and the number land together, so your transcription notes stay consistent.

Teach intervals in a music theory class

Put the calculator on the projector and let students predict the name before you reveal it. Enter C4 to E4 for a major 3rd, then C4 to Eb4 for a minor 3rd, and the one-semitone difference is right there on screen. The reference table doubles as a handout: every interval from minor 2nd to the octave with its semitone count and ratio.

Build a chord from a root note

You know you want a chord on D but cannot recall the spelling. Switch to build mode, set the root to D4, and step through the intervals: a major 3rd gives F#4, a perfect 5th gives A4. Three reads and you have a D major triad spelled out, ready to drop into a lead sheet or a DAW piano roll.

Check tuning against just intonation

When you compare equal temperament to pure ratios, the cents column is the bridge. A Perfect 5th reads 700 cents here, while the just 3:2 is about 702, so you can see the two-cent compromise that lets a piano play in every key. Useful when setting up a synth scale or explaining why a guitar never sounds perfectly in tune everywhere.

Music Interval Calculator for Notes, Semitones and Cents

Two notes in, the interval out: name, semitones, frequency ratio and cents, plus a reverse build from root plus interval

Runs locally
Category Calculator
Best for Getting a realistic range before a purchase, plan, workout, or schedule decision.

Root note

Target note

C4 → G4Perfect 5th

Semitones: 7
Frequency ratio (just): 3:2
Cents (equal temperament): 700 ¢

Common intervals (from C4)

Interval	Semis	To	Ratio
Perfect Unison	0	C4	1:1
Minor 2nd	1	C#4	16:15
Major 2nd	2	D4	9:8
Minor 3rd	3	D#4	6:5
Major 3rd	4	E4	5:4
Perfect 4th	5	F4	4:3
Tritone	6	F#4	45:32
Perfect 5th	7	G4	3:2
Minor 6th	8	G#4	8:5
Major 6th	9	A4	5:3
Minor 7th	10	A#4	16:9
Major 7th	11	B4	15:8
Perfect Octave	12	C5	2:1

What this tool does

A free music interval calculator that names the distance between any two notes and works backward from a root note plus an interval. Type two notes with octaves, like C4 and G4, and it reports the interval name (Perfect 5th), the semitone count (7), the just-intonation frequency ratio (about 3:2) and the size in cents (700). Flip to build mode, pick a root and an interval, and it returns the target note. Sharps and flats both parse, so C#4, Db4 and Bb3 all resolve to the right pitch. A reference table lists every common interval from minor 2nd to the octave with semitones, the note a step away from C4, and the classic ratio. One click copies a clean summary, and the shareable URL reopens with the exact notes and mode you set. Everything runs in your browser, with no upload and no account.

Tool details

Input: Numbers; The page exposes text boxes, numeric controls, file pickers, or structured inputs depending on the tool.
Output: Live result + Copy; The result area focuses on usable output, with copy, download, or preview actions when supported.
Privacy: Browser-side processing; The main tool logic does not call an external API, so inputs normally stay in the current tab.
Save / share: Shareable URL state; Key settings are encoded in the URL so another person can reopen the same setup.
Performance budget: Initial JS <= 9 KB; No WASM budget is declared, keeping the tool quick to open on mobile.
Best fit: Calculator · Content Creator; Category and role tags drive related tools, internal links, and quick fit checks.

How to use

1. Input

Paste or drop your content into the tool panel.
2. Process

Click the button. All processing is local in your browser.
3. Copy / Download

Copy the result or download to disk in one click.

How Music Interval Calculator fits into your work

Use it for fast estimates, comparisons, and planning numbers before you make the final call.

Calculation jobs

Getting a realistic range before a purchase, plan, workout, or schedule decision.
Comparing scenarios by changing one input at a time.
Turning rough assumptions into a number you can discuss.

Calculation checks

Double-check units, dates, rates, and rounding assumptions.
Treat health, finance, tax, and legal outputs as planning aids, not professional advice.
Save the inputs that produced an important result so you can reproduce it later.

Good next steps

These links move the current task into a more complete workflow.

Real-world use cases

Name an interval while transcribing by ear
You hear a leap in a melody and want to label it. Drop the two notes in, say A3 and E4, and the tool tells you it is a Perfect 5th, seven semitones. No counting half steps on a keyboard diagram or second-guessing whether that gap was a fourth or a fifth. The name and the number land together, so your transcription notes stay consistent.
Teach intervals in a music theory class
Put the calculator on the projector and let students predict the name before you reveal it. Enter C4 to E4 for a major 3rd, then C4 to Eb4 for a minor 3rd, and the one-semitone difference is right there on screen. The reference table doubles as a handout: every interval from minor 2nd to the octave with its semitone count and ratio.
Build a chord from a root note
You know you want a chord on D but cannot recall the spelling. Switch to build mode, set the root to D4, and step through the intervals: a major 3rd gives F#4, a perfect 5th gives A4. Three reads and you have a D major triad spelled out, ready to drop into a lead sheet or a DAW piano roll.
Check tuning against just intonation
When you compare equal temperament to pure ratios, the cents column is the bridge. A Perfect 5th reads 700 cents here, while the just 3:2 is about 702, so you can see the two-cent compromise that lets a piano play in every key. Useful when setting up a synth scale or explaining why a guitar never sounds perfectly in tune everywhere.

Common pitfalls

Forgetting the octave number. C and G without octaves are ambiguous; the tool needs C4 and G4 so it can tell a fifth up from a fourth down. Always include the digit after the letter and accidental.
Confusing a major third with a perfect fourth. A major 3rd is four semitones (C to E), a perfect 4th is five (C to F). One extra half step changes the name and the chord it implies, so read the semitone count, not just the note letters.
Treating cents and semitones as the same scale. A semitone is 100 cents, an octave is 1200. Writing 7 cents when you mean 7 semitones is off by a factor of a hundred; use semitones for naming intervals and cents only for fine tuning differences.

Privacy

Every step here is plain JavaScript running in your browser tab: parsing the note names, counting semitones, looking up the interval and ratio, and computing cents. No notes, intervals or results leave the page, and nothing is logged. The one caveat is the shareable URL, which encodes your two notes and the current mode in the query string, so a link pasted into chat will record those notes in the recipient server's access log. For private work, use the copy button and paste the text instead of sharing the URL.

FAQ

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Music Interval Calculator for Notes, Semitones and Cents

Common intervals (from C4)

What this tool does

Tool details

How to use

1. Input

2. Process

3. Copy / Download

How Music Interval Calculator fits into your work

Calculation jobs

Calculation checks

Good next steps

Real-world use cases

Name an interval while transcribing by ear

Teach intervals in a music theory class

Build a chord from a root note

Check tuning against just intonation

Common pitfalls

Privacy

FAQ

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