A Note Frequency in Every Octave
A runs from A0 at 27.50 Hz to A8 at 7040.0 Hz across the nine octaves of the chart. Because A4 at 440.00 Hz is the reference every other note is calculated from, the As are the only notes whose frequencies are exact in every octave, with nothing to round: halve or double 440 and you never leave the A column. The table below lists every A with its MIDI number, piano key and the name it gets in Yamaha-convention software.
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A in all 9 octaves
Every A from A0 to A8 at A4 = 440 Hz. Each name links to the full page for that note, with its tuning references, harmonics and intervals. The last column is the label the same key gets in software that calls middle C by the name C3.
| Note | Hz | MIDI | Piano key | Yamaha name |
|---|---|---|---|---|
| A0Lowest piano key | 27.50 | 21 | 1 | A-1 |
| A1 | 55.00 | 33 | 13 | A0 |
| A2 | 110.00 | 45 | 25 | A1 |
| A3 | 220.00 | 57 | 37 | A2 |
| A4Tuning reference | 440.00 | 69 | 49 | A3 |
| A5 | 880.00 | 81 | 61 | A4 |
| A6 | 1760.0 | 93 | 73 | A5 |
| A7 | 3520.0 | 105 | 85 | A6 |
| A8 | 7040.0 | 117 | off the piano | A7 |
Moving up one row doubles the frequency and moving down halves it. The 88-key piano runs from A0 to C8, so rows marked off the piano can only be played electronically.
Why A4 is the reference for every other note
Twelve tone equal temperament needs one fixed note, and that note is A4, the A above middle C. The modern standard puts it at 440.00 Hz, which is what ISO 16 specifies as the standard tuning frequency. A4 is MIDI note 69, so the formula for any note m is 440 x 2^((m - 69) / 12). Its neighbours an octave away are A3 at 220.00 Hz and A5 at 880.00 Hz.
A0 at 27.50 Hz is key 1, the lowest key of an 88-key piano, and the highest A on the keyboard is A7 at 3520.0 Hz (key 85). Ensembles that tune A4 higher or lower, for example to 442 Hz, shift every A in this table by the same ratio; the per-octave pages list each A at the other common references.
Why is A4 called A3 in some apps?
The MIDI specification fixes middle C as note number 60 but never says what to call the octave it sits in, so manufacturers picked different names for the same pitch. Scientific pitch notation, the convention this site uses, calls middle C by the name C4, and Roland chose the same labelling. Yamaha labelled note 60 as C3 instead, and plenty of DAWs and synths follow Yamaha. A few older programs call middle C by the name C5.
So A4 here, MIDI note 69 at 440.00 Hz, can read A3 on another screen. The pitch never changes, only the label: if your software shows every A one octave lower than the table above, it uses the Yamaha convention, and you convert by adding one to the octave number. When you need certainty, compare MIDI numbers or frequencies. The note frequency chart prints the MIDI number under every value for the same reason.
Which instruments have an open A string?
10 open strings in the TuneStand tuner registry are tuned to a A, from A1 up to A4.
| Instrument | String | Note | Hz |
|---|---|---|---|
| 5-String Bass | 3rd string (A) | A1 | 55.00 |
| Bass Guitar | 3rd string (A) | A1 | 55.00 |
| Double Bass | A string | A1 | 55.00 |
| 7-String Guitar | 5th string (A) | A2 | 110.00 |
| Guitar | 5th string (A) | A2 | 110.00 |
| Cello | A string | A3 | 220.00 |
| Mandolin | 2nd course (A) | A4 | 440.00 |
| Ukulele | 1st string (A) | A4 | 440.00 |
| Viola | A string | A4 | 440.00 |
| Violin | A string | A4 | 440.00 |
Frequently asked questions
Which A is 440 Hz?
A4, the A above middle C, is 440.00 Hz. It is MIDI note 69 and key 49 of an 88-key piano, and it is the standard tuning pitch set out in ISO 16. Yamaha-convention software labels the same key A3.
What is the lowest A on a piano?
A0 at 27.50 Hz is key 1, the lowest key of a standard 88-key piano. It is MIDI note 21. The highest A on the keyboard is A7 at 3520.0 Hz.
Why are the A frequencies exact numbers?
Because A4 is fixed at 440 Hz and every octave doubles or halves the frequency, so no rounding is involved. From A0 at 27.50 Hz upward each A is an exact multiple: A0 27.50 Hz, A1 55.00 Hz, A2 110.00 Hz, A3 220.00 Hz, A4 440.00 Hz, A5 880.00 Hz, A6 1760.0 Hz, A7 3520.0 Hz, A8 7040.0 Hz.
Is A4 the same as A3 in my DAW?
It can be. A DAW that follows the Yamaha convention calls middle C by the name C3 instead of C4, so the 440 Hz A shows up as A3. The pitch is the same MIDI note 69; only the octave number in the label differs.
Related notes and tools
Frequencies on this page are computed at build time from twelve tone equal temperament with A4 = 440 Hz, using the twelfth root of two (about 1.059463) per semitone. Nothing is typed in by hand. See the full method and sources. Maintained by FusionStudios. Last reviewed: .