A♯4 at a glance
All values assume twelve-tone equal temperament at the international standard pitch of A4 = 440 Hz. In that system every semitone has the same size - a frequency ratio of 2^(1/12) - so A♯4 is exactly 440 × 2^(1/12) Hz. Under alternative references the note shifts with the reference: at A4 = 432 Hz, A♯4 becomes 457.69 Hz.
A♯ in every octave
| Note | Frequency | MIDI | Piano key |
|---|---|---|---|
| A♯0 | 29.14 Hz | 22 | 2 |
| A♯1 | 58.27 Hz | 34 | 14 |
| A♯2 | 116.54 Hz | 46 | 26 |
| A♯3 | 233.08 Hz | 58 | 38 |
| A♯4 ← | 466.16 Hz | 70 | 50 |
| A♯5 | 932.33 Hz | 82 | 62 |
| A♯6 | 1864.7 Hz | 94 | 74 |
| A♯7 | 3729.3 Hz | 106 | 86 |
Each octave doubles the frequency - the simplest relationship in music, and the reason notes an octave apart sound like “the same note, higher”.
Neighboring notes
One semitone down is A4 at 440.00 Hz; one semitone up is B4 at 493.88 Hz. Need a frequency between notes, or a different waveform? The tone generator plays anything from 20 Hz to 20 kHz; the note ↔ frequency converter does the math both directions, and the chromatic tuner listens to your instrument and shows the offset in cents.