Reference tone
440 Hz — Concert Pitch (A4)
440 Hz is A4 — the note orchestras, pianos and tuners calibrate to. It's the international concert-pitch standard (ISO 16).
Tap a note to play its exact pitch — C1 to B8
Press Space to play
About the 440 Hz tone
When someone says an instrument is at “standard tuning” or “concert pitch”, they almost always mean A = 440 Hz. It's the reference nearly every electronic tuner, keyboard and tuning app defaults to.
To tune by ear, play this tone and match your A (the A above middle C) until the two stop “beating” against each other — the wavering pulse you hear when two pitches are close but not identical disappears when they line up.
If you play along with older recordings or certain ensembles, check whether they use 440 or a nearby reference such as 432 or 442 — matching the source matters more than the exact number.
Technical details
- Frequency
- 440 Hz
- Nearest note
- A4 (in tune)
- Category
- Reference tone
- Period
- 2.27 ms
- Wavelength (air)
- 78.0 cm
- Octave up / down
- 880 Hz / 220 Hz
Common uses
- Tune guitar, violin, piano or wind instruments to standard pitch
- Check or calibrate a tuner or tuning app
- Interval and pitch ear-training against a fixed reference