Free Online Piano Note Frequency Finder
Find frequencies for every piano key and octave.
The keyboard spans C3 to B5. Click a key to hear its equal-tempered pitch and see its frequency and MIDI number. Black keys are labelled with their sharp names.
About the Piano Note Frequency Finder
A piano keyboard is a map of musical pitch. Each key corresponds to a frequency, and each octave doubles the frequency of the one below it. This interactive keyboard spans three octaves from C3 to B5 and reports the note name, exact equal-tempered frequency, MIDI number, and cents deviation from standard A440 tuning. It is useful for composers, producers, piano tuners, and anyone who wants to connect the visual layout of a keyboard with the underlying mathematics of pitch.
Why the black keys are uneven
The white keys form the C major scale, and the black keys fill in the semitones between them. The pattern of two black keys followed by three black keys reflects the positions of the half steps in the diatonic scale. Between E and F, and between B and C, there is no black key because those pairs are already separated by a single semitone. This layout is a physical representation of the equal-tempered scale, where every adjacent key, white or black, represents the same frequency ratio of about 1.059463.
Frequency and MIDI
The MIDI standard assigns a number to every semitone, with middle C usually numbered 60. The frequency of a MIDI note is f = 440 × 2(n − 69) / 12, where 69 is A4. The formula works in both directions: higher MIDI numbers produce higher frequencies, and every increase of twelve doubles the frequency. A piano's lowest key, A0, is MIDI 21 at about 27.5 Hz, while C8 is MIDI 108 at about 4186 Hz. This page covers a practical middle range where most melodic writing happens.
Equal temperament versus pure intervals
Equal temperament divides the octave into twelve identical semitone ratios so that instruments can play in any key without retuning. The trade-off is that most intervals are slightly wider or narrower than their pure harmonic counterparts. A pure perfect fifth has a frequency ratio of 3:2, but the equal-tempered fifth is about two cents narrow. Piano tuners often stretch the octaves slightly to compensate for the inharmonicity of real strings, which is why a tuned piano may not match the mathematical formula exactly across its full range.
Using the keyboard
- Click any white or black key to hear its tone and update the readout.
- Change the A4 reference to explore historical or orchestral pitch standards.
- Use the cents readout to see how a non-440 reference compares with standard equal temperament.
- Adjust the volume before playing; synthesised tones can be loud through headphones.
- Use the play button to repeat the selected note without clicking the key again.
Frequently asked questions
Why does C4 have a frequency of about 261.63 Hz?
C4 is nine semitones below A4. Applying the equal-tempered ratio nine times to 440 Hz gives approximately 261.63 Hz. The exact value depends on the A4 reference.
Are the black keys always sharps?
They can be written as sharps or flats depending on the musical context. This tool uses sharp names for simplicity, so C♯ and D♭ refer to the same key.
Can I use this to tune a piano?
It provides accurate equal-tempered reference pitches, but professional piano tuning also requires adjusting for inharmonicity, stretch, and the specific instrument. Use a dedicated tuning app or a qualified technician for a real piano.