Musical Interval Calculator

MIDI numbering turns every pitch into a single integer that increases by exactly one per semitone across the entire range, which makes finding the distance between any two notes as simple as subtracting one number from the other regardless of which octave each note falls in. Converting note-and-octave pairs into this common numbering system first is what lets the calculator handle notes in different octaves correctly without special-casing octave boundaries.

The interval spanning exactly 6 semitones sits precisely halfway between a perfect 4th and a perfect 5th in 12-tone equal temperament, and depending on how the notes are spelled in traditional notation it can correctly be called either an augmented 4th or a diminished 5th — both describe the identical sound. This calculator, working from raw semitone counts rather than note spelling, can't distinguish which name applies and reports it generically rather than guessing.

It counts how many full octaves the semitone distance spans, then adds that many multiples of 7 to the base interval number, since each additional octave shifts a 2nd into a 9th, a 3rd into a 10th, and so on. This mirrors how musicians actually name wide intervals — a 9th is understood as an octave plus a step, not as an entirely different category of interval from a 2nd.

No — a major sixth ascending from C to A and a major sixth descending from C down to the E below it are both still major sixths in name and quality, since interval quality and number describe the relationship's shape regardless of which note came first. Direction is reported separately purely to indicate which note is higher, which matters for melodic analysis even though it doesn't change how the interval itself is classified.