How to Check Your Piano
- Tap Start Tuning and put your device on the music stand.
- Play one key at a time, firmly, and hold it down. Start with A4, the A above middle C, then check a few notes across the keyboard, such as C2, C3, C4, C5, and C6.
- Note how many cents each one is off. Within about 5 cents is fine for most listeners.
What the Readings Mean
- Every note is flat by a similar amount: the whole piano has sagged in pitch, which is common if it hasn't been tuned for a year or more. A technician can bring it back to 440 Hz with a pitch raise before the tuning.
- Some notes are off and others are fine: the piano is due for a regular tuning.
- One note sounds wavy or sour even though its reading looks right: most keys have two or three strings, and one of them has slipped. The tuner hears their average, so this needs a technician.
Why an App Can't Tune a Piano
Piano tuning is more than matching each note to a number. Technicians tune with stretch, setting the high notes slightly sharp and the low notes slightly flat so octaves sound right, and they set each key's two or three strings exactly together. Use this page to check your piano, and book a professional for the tuning itself. Most pianos need tuning once or twice a year.
Piano Note Frequencies
Landmark keys on an 88-key piano at A4 = 440 Hz, in equal temperament.
| Key | Frequency |
|---|---|
| A0 (lowest key) | 27.50 Hz |
| C1 | 32.70 Hz |
| C2 | 65.41 Hz |
| C3 | 130.81 Hz |
| C4 (middle C) | 261.63 Hz |
| A4 | 440.00 Hz |
| C5 | 523.25 Hz |
| C6 | 1046.50 Hz |
| C7 | 2093.00 Hz |
| C8 (highest key) | 4186.01 Hz |