Piano note
A4 Piano Note Frequency
A4 is key 49 of the 88 on a standard piano, with a frequency of 440.00 Hz when the piano is tuned to A4 = 440 Hz.
440.00 Hz
A4 at a glance
- Frequency (A4 = 440 Hz)
- 440.00 Hz
- At A4 = 442 Hz
- 442.00 Hz
- At A4 = 432 Hz
- 432.00 Hz
- Piano key number
- 49 / 88
- MIDI note number
- 69
- Octave
- 4
- Key colour
- White key
- Wavelength in air
- 78.0 cm
- Period (one vibration)
- 2.27 ms
- Register
- Middle
Wavelength assumes sound travels at 343 m/s (air at about 20 °C).
About this part of the keyboard
A4 is the concert-pitch reference: tuning it to 440 Hz is the international standard (ISO 16), and tuners usually set it first.
This is the heart of the keyboard around middle C. On most pianos each note here has three plain steel strings (a trichord) that must match each other exactly. Tuners usually start here, setting the temperament octave and A4 before tuning the rest of the piano from it.
Neighbouring keys
Is your A4 in tune?
Play A4 on your piano and our free online tuner will show how many cents it is from 440.00 Hz.
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