A4 — 440.00 Hz
A4 (MIDI 69) vibrates 440.00 times per second at standard concert pitch. Play the reference tone below, or tune to it with the online tuner.
A4 at different reference pitches
| Reference (A4) | A4 frequency | Used for |
|---|---|---|
| 415 Hz | 415.00 Hz | Baroque pitch |
| 432 Hz | 432.00 Hz | “Verdi” pitch |
| 440 Hz | 440.00 Hz | Standard concert pitch |
| 442 Hz | 442.00 Hz | European orchestras |
| 444 Hz | 444.00 Hz | European orchestras |
Physical properties
- Period: one cycle every 2.27 ms
- Wavelength in air: ≈ 78.0 cm (at 20 °C, 343 m/s)
- MIDI note number: 69
- Octave up: A5 = 880.00 Hz · Octave down: 220.00 Hz