Loading page
About this tool
Name the interval between any two notes, with semitone distance, cents, inversion and the just-intonation ratio.
A musical interval is named by two things: the number of staff degrees the two notes occupy, and how the actual semitone distance compares with the major or perfect size of that number. This calculator applies both rules, so C to F# comes back as an augmented fourth while C to Gb comes back as a diminished fifth even though each spans six semitones. It also reports cents, the inversion, the equal-tempered frequency ratio and the five-limit just ratio the interval is tuned against.
Open Music Interval Calculator on AltFTool — it loads instantly in your browser.
Set the First note and Second note with the Letter, Accidental and Octave dropdowns, or tap a preset like Perfect fifth, Tritone or Major tenth; adjust 'Concert pitch, A4 (Hz)' if you need non-440 tuning.
The calculator names the interval from staff spelling, not just semitones — C to F# reads as an augmented fourth while C to Gb reads as a diminished fifth, both at six semitones.
Read the Semitones, Cents (12-TET), frequency ratio, pure (just) ratio with its tempering error, Inversion and MIDI numbers rows, then press Copy result to copy the breakdown.
Enharmonic pairs like F# and Gb produce different interval names, as they should.
The same interval is shown as semitones, cents, a decimal ratio and a whole-number just ratio.
Every simple interval is paired with its inversion, so a minor sixth immediately reads as a major third.
Count the letter names inclusively to get the number, then compare the semitone distance with the major or perfect size of that number to get the quality. C up to E covers C-D-E, so it is a third; it spans 4 semitones, which is the major size, making it a major third.
Within one octave: minor 2nd 1, major 2nd 2, minor 3rd 3, major 3rd 4, perfect 4th 5, tritone 6, perfect 5th 7, minor 6th 8, major 6th 9, minor 7th 10, major 7th 11 and perfect octave 12. Compound intervals add 12 semitones per extra octave, so a major tenth is 16.
They sound identical in equal temperament — both are 6 semitones — but they are spelled and resolved differently. An augmented fourth (C to F#) is a fourth widened by a semitone and tends to expand outward; a diminished fifth (C to Gb) is a fifth narrowed by a semitone and tends to contract inward.
Equal temperament makes every semitone exactly 100 cents so all keys are usable, which forces most intervals off their whole-number ratios. The pure major third is 5:4, about 386.31 cents, while the tempered major third is 400 cents — roughly 13.7 cents sharp. The tempered fifth is much closer, only about 1.96 cents flat of 3:2.
Add the Music Interval Calculator widget to your blog or website — free, responsive, no signup. Just keep the “Widget by AltFTool” credit link visible.
<iframe src="https://www.altftool.com/embed/widget/music-interval-calculator"
title="Music Interval Calculator — free AltFTool widget"
width="100%" height="640" style="border:0;border-radius:12px;overflow:hidden"
loading="lazy" referrerpolicy="no-referrer-when-downgrade" allow="clipboard-write"></iframe>
<p style="font-size:12px;margin:4px 0 0">Widget by <a href="https://www.altftool.com/tools/all/music-interval-calculator?utm_source=embed&utm_medium=widget" rel="nofollow">AltFTool — free online tools</a></p>