Interval between two notes calculator

It reports the interval number, quality, abbreviation, direction, and semitone span. Because spelling matters in music theory, the calculator reads the letter names as well as the sounding distance: F-sharp to C is a diminished fifth, while F-sharp to B-sharp is an augmented fourth. It also handles descending and compound intervals without replacing them with simpler enharmonic names.

Enter spelled notes, not just piano keys

Choose the first and second note exactly as they appear in the music, then supply an octave for each using scientific pitch notation, where middle C is C4. You may use natural notes, sharps, flats, double sharps, or double flats. The spelling is essential because an interval has two independent dimensions: its number counts written letter positions, while its quality compares the actual semitone span with the expected span for that number. C4 to F-sharp4 and C4 to G-flat4 sound the same in equal temperament, but the first is an augmented fourth and the second is a diminished fifth. A tool that looks only at piano keys cannot preserve that distinction. The octave fields remove another ambiguity. C4 to C5 is a perfect octave, whereas C4 to C4 is a perfect unison. Entering both octaves also lets the calculator recognize direction and compound intervals instead of reducing every answer to one octave. Use the notation on the score rather than respelling a note to a more familiar enharmonic equivalent.

How quality and number are calculated

The interval number is found by counting staff letters inclusively from one note to the other. C to E includes C, D, and E, so it is some kind of third; C to F includes four letters, so it is some kind of fourth. Octave changes extend that count, producing ninths, tenths, elevenths, and other compound intervals. The calculator then finds the absolute chromatic distance in semitones, including each accidental. For unisons, fourths, fifths, and their compound equivalents, the reference quality is perfect. For seconds, thirds, sixths, sevenths, and their compounds, the wider reference is major and one semitone narrower is minor. Expanding a perfect or major reference by one semitone makes it augmented. Contracting a perfect reference by one semitone makes it diminished; contracting a minor interval by one more semitone does the same. The result therefore follows conventional written interval theory rather than choosing a label from a twelve-entry chromatic table. The semitone total is returned as supporting information, while the quality and number remain the primary answer.

Read descending and compound results correctly

Direction is based on sounding pitch after the octaves and accidentals are applied. If the second pitch is lower, the result is marked descending, but the interval name still describes the inclusive distance between the two written notes. For example, E5 down to C5 spans a minor third. Compound intervals retain their full number: C4 to E5 is a major tenth, not merely a major third, because the octave placement is part of the question. This is useful when checking vocal ranges, orchestration, counterpoint exercises, chord voicings, and transcriptions where register matters. The abbreviation combines the conventional quality symbol with the complete number, such as P5, m3, A4, or M10. Enharmonically equivalent notes can intentionally produce different names, and that is expected rather than an error. If the written staff direction and sounding direction conflict because extreme accidentals reverse the pitches, the calculator asks you to check the entry instead of returning a misleading theoretical label. API requests use the same deterministic calculation as the browser tool and cost $0.002 per request.