# Cent (music)

The

**cent** is a

logarithmic measure of relative

pitch or

intervals. 1200 cents are equal to one

octave, and an

equally tempered semitone is equal to 100 cents. The formula to determine the value in cents between two notes with

frequencies *a* and

*b* is:

The measure was developed by A. J. Ellis around the

1870s, and was published in his edition of

Hermann von Helmholtz's

*On the Sensations of Tone*. It has since become the standard way of measuring intervals in

equal temperament systems or for comparison with equal temperament systems.

See also: *music*