Music Interval Calculator
Name the interval between two notes, with ratios and inversion.
About this tool
Choose two notes, each with a letter, accidental and octave. The tool names the interval from its spelling, counts the semitones, gives the equal-tempered and just ratios in cents, and shows the inversion. Play both notes to hear it.
How intervals are named
An interval has a number and a quality. The number counts letter names inclusively: C up to E is a 3rd (C, D, E), C up to G a 5th. The quality depends on the exact semitones. Unisons, 4ths, 5ths and octaves are perfect; 2nds, 3rds, 6ths and 7ths are major or minor; any interval can be augmented (one semitone wider) or diminished (one narrower). Spelling matters: C–E♭ and C–D♯ both span 3 semitones, but the first is a minor 3rd and the second an augmented 2nd. C–F♯ (augmented 4th) and C–G♭ (diminished 5th) are both the 6-semitone tritone. Intervals wider than an octave are compound: C4 to D5 is a major 9th. The tool also compares equal temperament with just intonation: a pure major 3rd (5:4) is 386 cents, while a piano's is 400. Inversions flip an interval: major becomes minor, augmented becomes diminished, and the numbers add up to 9. The note frequency calculator and the ear trainer are related.
Frequently asked questions
What interval is C to E?
A major 3rd: four semitones.
What is the difference between an augmented 4th and a diminished 5th?
Both are six semitones (a tritone), but they're spelled differently: C–F♯ is an augmented 4th, C–G♭ a diminished 5th.
How do you invert an interval?
Subtract the number from 9 and swap the quality: a major 3rd inverts to a minor 6th, a perfect 4th to a perfect 5th.
What is a compound interval?
One wider than an octave, such as a 9th (an octave plus a 2nd) or a 10th (an octave plus a 3rd).
Is my data sent anywhere?
No. Everything is calculated in your browser, and nothing is stored or sent.