Interval Reference
Every interval within the octave — its name, size in semitones and cents, the just-intonation ratio, and an example built from C.
| Semitones | Interval | Short | Cents (ET) | Just ratio | From C |
|---|---|---|---|---|---|
| 0 | Perfect unison | P1 | 0 | 1/1 | C |
| 1 | Minor second | m2 | 100 | 16/15 | D♭ |
| 2 | Major second | M2 | 200 | 9/8 | D |
| 3 | Minor third | m3 | 300 | 6/5 | E♭ |
| 4 | Major third | M3 | 400 | 5/4 | E |
| 5 | Perfect fourth | P4 | 500 | 4/3 | F |
| 6 | Tritone | TT | 600 | 45/32 | F♯ / G♭ |
| 7 | Perfect fifth | P5 | 700 | 3/2 | G |
| 8 | Minor sixth | m6 | 800 | 8/5 | A♭ |
| 9 | Major sixth | M6 | 900 | 5/3 | A |
| 10 | Minor seventh | m7 | 1000 | 16/9 | B♭ |
| 11 | Major seventh | M7 | 1100 | 15/8 | B |
| 12 | Perfect octave | P8 | 1200 | 2/1 | C |
Cents are equal-temperament (100 per semitone); just ratios are the small-integer ratios of just intonation. Measure the interval between any two notes with the interval calculator.
How to read this
An interval has two parts: a size in semitones, and a name that depends on how the notes are spelled.
0 unison · 1 m2 · 2 M2 · 3 m3 · 4 M3 · 5 P4
6 tritone · 7 P5 · 8 m6 · 9 M6 · 10 m7 · 11 M7 · 12 octaveC–D♯ and C–E♭ are both three semitones, but one is an augmented second and the other a minor third.
Notes & gotchas
- Inversions sum to nine. A third inverts to a sixth, a fourth to a fifth — and major becomes minor, perfect stays perfect.
- The tritone inverts to itself, which is the source of both its instability and its usefulness for modulation.
- Learn them by song. Perfect fifth: Twinkle, Twinkle. Minor third: a doorbell. Far faster than counting semitones.
- Spelling matters for notation, not pitch. In code, work in semitones modulo 12 and convert to names only for display.