MIDI to Frequency Converter
Convert in any direction: type a MIDI note number, a
note name such as C4 or F#3, or a
frequency in hertz. The other two fields update instantly, and the note lights
up on the keyboard below.
Whole numbers from 0 (C−1) to 127 (G9). An 88-key piano covers 21–108.
Letter, optional accidental (# or b), then octave number.
Any positive frequency. You will get the nearest note plus the offset in cents.
Note details
| Nothing entered yet. |
On the keyboard
Click any key to load that note. The keyboard spans A0 to C8 — the 88 keys of a standard piano.
How the conversion works
Modern instruments use twelve-tone equal temperament, which splits the octave into twelve equal semitones. With A4 fixed at 440 Hz, the frequency of MIDI note m is:
f = 440 × 2(m − 69) / 12
Going the other way — from hertz back to a note number:
m = 69 + 12 × log2(f / 440)
Worked example. Take MIDI 60, middle C:
f = 440 × 2(60 − 69) / 12 = 440 × 2−0.75 = 261.63 Hz
Because each step of 12 doubles the frequency, MIDI 72 (C5) is exactly
261.63 × 2 = 523.25 Hz.
Landmark MIDI numbers
| MIDI | Note | Frequency (Hz) | Why it matters |
|---|---|---|---|
| 21 | A0 | 27.50 | Lowest key on an 88-key piano |
| 40 | E2 | 82.41 | Lowest open string, guitar in standard tuning |
| 60 | C4 | 261.63 | Middle C — the usual reference point |
| 69 | A4 | 440.00 | International tuning standard (ISO 16) |
| 88 | E6 | 1318.51 | Top of the treble staff's practical range |
| 108 | C8 | 4186.01 | Highest key on an 88-key piano |
Frequently asked questions
- How do you convert a MIDI note number to hertz?
- Use
f = 440 × 2(m − 69) / 12, where m is the MIDI number. MIDI 69 is A4 at 440 Hz, and every increase of 12 doubles the frequency. - What MIDI number is middle C?
- Middle C is MIDI note 60 — C4 at 261.63 Hz. Yamaha and some DAWs label it C3, but the MIDI number is always 60.
- How do I find the MIDI note for a frequency?
- Use
m = 69 + 12 × log2(f / 440)and round to the nearest whole number. This converter does it for you and also reports how many cents the input sits away from the nearest note. - What note names does the converter accept?
- Scientific pitch notation such as
C4,F#3orBb2. Sharps accept#or the sharp sign, flats accept a lowercasebor the flat sign. Letters are not case sensitive. - What does the cents figure mean?
- A cent is one hundredth of a semitone. If you enter a frequency that does not land exactly on an equal-tempered note, the cents value tells you how far off it is — useful for checking tuning.
- Is my data uploaded anywhere?
- No. The calculation runs entirely in your browser; nothing is sent to a server.
Last updated: 2026-09-01