Music · Piano
Piano key frequency chart.
All 88 keys with their note names and frequencies in hertz, plus a lookup from key number. Change the A4 reference if your piano or ensemble tunes to something other than 440 Hz.
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What frequency is each piano key?
On an idealized 88-key piano in twelve-tone equal temperament the 49th key, A4, is tuned to 440 Hz and each key up multiplies the frequency by the twelfth root of two. For key n: f = 440 × 2(n − 49) / 12 Hz. Going the other way, n = 12 × log2(f / 440) + 49.
Worked example. Middle C is key 40: 440 × 2(40 − 49) / 12 = 261.63 Hz. The lowest key, A0, is 27.50 Hz and the highest, C8, is 4186.01 Hz. Twelve keys up always doubles the frequency, so A5 (key 61) is 880 Hz.
Real pianos are not exactly equal. The string stiffness makes each note’s overtones run slightly sharp, so tuners stretch the octaves slightly wide. The table is the idealized equal-temperament value, which is the right reference for synths, tuners and software.
Frequently asked questions
What is the frequency of middle C?
Middle C (C4, key 40) is 261.63 Hz when A4 is 440 Hz.
What is the lowest and highest piano note in Hz?
A0 is 27.5 Hz and C8 is 4186.01 Hz.
How do I calculate the frequency of a piano key?
f = 440 x 2^((n - 49) / 12), where n is the key number from 1 to 88 and key 49 is A4.
Can I change the A4 reference to 442 Hz?
Yes. Enter any value from 400 to 480 Hz and the whole table rescales in proportion.
Does a real piano match these numbers exactly?
Not quite. Real pianos are tuned with slightly stretched octaves because of string inharmonicity. These are the ideal equal-temperament values.
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