A4 is usually tuned to 440 Hz.
Frequency chart
Piano key frequency chart
A piano key frequency chart shows the pitch of each key in hertz. With standard tuning, A4 is 440 Hz and Middle C is about 261.63 Hz.
C3D3E3F3G3A3B3C4D4E4F4G4A4B4C5
C#3D#3F#3G#3A#3C#4D#4F#4G#4A#4Middle C is about 261.63 Hz in standard tuning.
One octave higher doubles the frequency.
What frequency means
Frequency is the speed of vibration measured in hertz. Higher notes vibrate faster than lower notes.
Why A4 is the tuning reference
Pianos and digital instruments commonly use A4 as the reference pitch. The rest of the notes are calculated from that tuning point.
How octaves change frequency
If a note moves up one octave, its frequency doubles. If it moves down one octave, its frequency halves.
Common piano key frequencies at A4=440
| Note | MIDI | Frequency |
|---|---|---|
| C3 | 48 | 130.81 Hz |
| C4 | 60 | 261.63 Hz |
| E4 | 64 | 329.63 Hz |
| G4 | 67 | 392.00 Hz |
| A4 | 69 | 440.00 Hz |
| C5 | 72 | 523.25 Hz |
FAQ
Quick answers
What frequency is Middle C?
Middle C is about 261.63 Hz when A4 is tuned to 440 Hz.
What frequency is A4?
A4 is usually 440 Hz in standard tuning.
Does every piano use A4=440?
Most modern reference charts use A4=440, but some ensembles or historical tunings use a different A4 value.