How to use it
- Type the first note with its octave, for example C4, Bb3 or F#5.
- Type the second note. If you leave out both octaves, the second note is taken above the first.
- Read the interval name, its short form (P5, M3, m7), the semitones, cents and ratios.
How it works
- Number: letters from the lower to the higher note, both counted (C → G: C D E F G = 5).
- Quality: semitones compared with the major or perfect interval of that number. One semitone more than major or perfect is augmented; one less than minor or perfect is diminished.
- Equal-tempered ratio: 2^(semitones ÷ 12); cents = semitones × 100.
- Just ratio: the usual five-limit ratios (1:1, 16:15, 9:8, 6:5, 5:4, 4:3, 45:32 or 64:45, 3:2, 8:5, 5:3, 9:5, 15:8, 2:1), doubled for each octave.
Worked example
C4 to G4:
- letters C D E F G → a fifth;
- 7 semitones, the same as a perfect fifth → Perfect fifth (P5);
- 700 cents; equal-tempered ratio 2^(7/12) = 1.4983; just ratio 3:2 = 701.96 ¢;
- inversion: G to C, a Perfect fourth (P4).
Tips
- Use the spelling from the score: E–G♯ (major third) and E–A♭ (diminished fourth) read differently.
- Compound intervals keep their full name up to a double octave: C4–E5 is a Major tenth.
- To go from cents to frequencies and back, use the cents calculator.