A0 at every common reference pitch
A note’s frequency depends on what A4 is tuned to. The standard is 440 Hz; the other three are the ones you are most likely to meet. The cents column is how far each one sits from the 440 version — the same for every note, because changing the reference moves the whole scale together.
| Reference | A0 | vs 440 |
|---|---|---|
| A4 = 415 Hz · Baroque pitch | 25.94 Hz | −101.3¢ |
| A4 = 432 Hz · “Verdi” pitch | 27.00 Hz | −31.8¢ |
| A4 = 440 Hz · Standard (ISO 16) | 27.50 Hz | — |
| A4 = 442 Hz · Orchestral | 27.63 Hz | +7.9¢ |
One cycle of A0 lasts 36.364 ms, and its wavelength in air at 20 °C is 12.47 m. Hold it as a steady tone in the tone generator.
A0 on the piano
A0 is key 1 of 88, counting from the bottom — a white key. Press any key below to compare it with its neighbours.
A0 on the guitar
A0 is below the guitar’s lowest note, the open low E (E2), so a guitar in standard tuning cannot play it.
A0 on the staff
Instruments that can play A0
1 instrument plays A0 within the normal range, and 1 reach it only at the extreme of theirs. Each links to its range chart; for a transposing instrument, the note on its part is shown.
Keyboards and free reeds
Only at the extreme of their range
A0 is outside the typical range of all six voice types. Test your own range.
The harmonics of A0
A played A0 is not one frequency. A string or a pipe also sounds whole-number multiples of it, and the mix of those harmonics is the instrument’s tone. Here is where the first eight land — and why the 7th sounds out of tune against a piano.
| Harmonic | Frequency | Nearest note | Off by |
|---|---|---|---|
| 1 (fundamental) | 27.50 Hz | A0 | 0¢ |
| 2 | 55.00 Hz | A1 | 0¢ |
| 3 | 82.50 Hz | E2 | +2.0¢ |
| 4 | 110.00 Hz | A2 | 0¢ |
| 5 | 137.50 Hz | C♯3 | −13.7¢ |
| 6 | 165.00 Hz | E3 | +2.0¢ |
| 7 | 192.50 Hz | G3 | −31.2¢ |
| 8 | 220.00 Hz | A3 | 0¢ |
Frequently asked questions
What is the frequency of A0?
A0 is 27.50 Hz in equal temperament with A4 tuned to 440 Hz, the international standard. At A4 = 432 Hz it is 27.00 Hz, and at the orchestral A4 = 442 Hz it is 27.63 Hz.
Which octave is A0 in?
The number is the octave in scientific pitch notation, where each octave starts on C and C4 is middle C. A0 is in octave 0, 39 semitones below middle C. In Helmholtz notation, used in older books, it is written A₂.
How do I play A0 on a piano?
A0 is key 1 of 88, counting from the bottom — a white key.
Which instruments can play A0?
1 of the instruments we chart play A0 within their normal range, including piano, and 1 more reach it only at the extreme of their range.
Typing it? A0 is also written A0. Convert any frequency on the Hz-to-note converter.