The frequency 440.2542274 Hz is 1 cent above A4: The formula above gives n b = 100.0008857 ≈ 100 cents To calculate the bias from a note in cents n b from known frequency f n, we will use the following formula:įor example, A4♯/B4♭ has the frequency of 466.164 Hz. In other words, one cent is 1/100 of a semitone. The cent is a dimensionless logarithmic unit of measurement of musical intervals defined as the ratio of two frequencies f 1 and f 2, which is equal to:ġ00 cents make one semitone of the equal-tempered scale. Note that the ratio of the frequencies of the two notes in any semitone interval a is equal to the twelfth root of 2: There are 88 notes in the standard piano keyboard, from note A0 (sub-contra octave), which is the piano note 0 with a frequency of 27.500 Hz, to note C8, which is the piano note 88 with a frequency of 4186.009 Hz.

To calculate frequencies of musical notes from known standard (88-key) piano note number n p and the standard pitch A440, and vice versa, we can use the following formulas: There are 128 notes in the MIDI standard (0 to 127), from the note C–1 (minus 1), which is the MIDI note 0 with a frequency of 8.176 Hz, to the note G9, which is the MIDI note 127 with a frequency of 13289.750 Hz. To calculate frequencies of musical notes from known MIDI note number n m and the standard pitch A440, and vice versa, we can use these formulas: The formula above can be modified to calculate the number n of semitones away from the standard pitch f 0: N is the number of semitones (half steps) from the standard pitch n > 0 for notes higher than the standard pitch, and n < 0 for notes lower than the standard pitch.

It is usually a standard (also called concert) pitch of 440 Hz, which is called A440 or note A in the one-line (or fourth) octave (A4) The basic formula to calculate frequencies of musical notes of the equal-tempered scale:į n is the frequency of the note, which is n semitones (or half steps) away from the standard pitch A440 į 0 is the frequency of a fixed note, which is used as a standard for tuning.

Audio to midi note number