Cents Difference Calculator

Two notes sound nearly identical and you need to say how far apart they are in musical terms, not in hertz. Hertz will not do it: two hertz is a noticeable gap near A440 and almost nothing up in the high register. Cents fix that, because the scale is logarithmic and the same perceived distance yields the same number anywhere. Type the two frequencies and read the difference below.

The formula is 1200 times the base-2 logarithm of f2 divided by f1. The 1200 comes from splitting the octave into 1200 parts, which makes each equal-tempered semitone worth exactly 100 cents. With 440 and 442 you get 7.851415 cents, a gap a trained ear will catch but nowhere near a semitone. Field order matters: if f2 is smaller than f1, the answer comes out negative.

Some anchors for reading the number: around 5 cents is where most listeners start hearing sustained notes as out of tune, a just major third sits 14 cents below the tempered one, and baroque pitch at 415 Hz is 101.27 cents away from 440, nearly a full semitone. Zero or negative frequencies show a dash. This is not a tuner, there is no microphone and no pitch detection, just the calculation, done in your browser.