Piano key frequencies

This is a list of the fundamental frequencies in hertz (cycles per second) of the keys of a modern 88-key standard or 108-key extended piano in twelve-tone equal temperament, with the 49th key, the fifth A (called A4), tuned to 440 Hz (referred to as A440).

On an actual piano, the ratio between semitones is slightly larger, especially at the high and low ends, where string stiffness causes inharmonicity, i.e., the tendency for the harmonic makeup of each note to run sharp.

To compensate for this, octaves are tuned slightly wide, stretched according to the inharmonic characteristics of each instrument.

[3] This deviation from equal temperament is called the Railsback curve.

[1] Conversely, the key number of a pitch with a frequency f (Hz) on the idealized standard piano is: Values in bold are exact on an idealized standard piano.