MIDI Note to Frequency Calculator
Convert MIDI note numbers to frequency (Hz) and back.
Supports any tuning reference (A4 = 440 Hz default).
Find note names, octaves, and cents offsets.
MIDI Note Numbers
The MIDI standard assigns each semitone an integer from 0 to 127. Middle C is MIDI 60. The pitch standard A4 (concert A) is MIDI 69, conventionally tuned to 440 Hz.
Formulas
Frequency from MIDI:
f = f_ref × 2^((n − n_ref) / 12)
Default: f_ref = 440 Hz, n_ref = 69 (A4).
MIDI from frequency:
n = n_ref + 12 × log₂(f / f_ref)
If n is not an integer, the fractional part is a cents offset from the nearest tempered note.
Common MIDI Notes
| MIDI | Note | Frequency (440 Hz tuning) |
|---|---|---|
| 21 | A0 (lowest piano) | 27.5 Hz |
| 36 | C2 | 65.4 Hz |
| 48 | C3 | 130.8 Hz |
| 60 | C4 (middle C) | 261.6 Hz |
| 67 | G4 | 392.0 Hz |
| 69 | A4 (concert A) | 440.0 Hz |
| 72 | C5 | 523.3 Hz |
| 84 | C6 | 1046.5 Hz |
| 96 | C7 | 2093.0 Hz |
| 108 | C8 (top piano) | 4186.0 Hz |
| 127 | G9 | 12544 Hz (highest MIDI) |
Octave Numbering
MIDI uses scientific pitch notation: middle C is C4 (some DAWs use C3 — always check your software). Each octave covers 12 MIDI numbers, so:
- C0 = 12, C1 = 24, C2 = 36, C3 = 48, C4 = 60, C5 = 72, C6 = 84
Tuning References
Concert pitch A4 = 440 Hz is the international standard, but historical and ensemble pitches differ:
| Reference | A4 (Hz) | Era / Use |
|---|---|---|
| Verdi tuning | 432 | Some early Italian opera, philosophical movements |
| Baroque pitch | 415 | Period instrument performance |
| Classical A | 430 | Mid-18th to early 19th century orchestras |
| Modern standard | 440 | Adopted internationally 1939 |
| Modern bright | 442–444 | Many European orchestras today |
This calculator lets you specify any A4 reference and recompute frequencies accordingly.
Cents Offset
If a measured frequency does not fall exactly on a MIDI note, the offset in cents is:
cents = 1200 × log₂(f_measured / f_nearest_note)
Skilled musicians detect about 5 cents. Modern auto-tune algorithms work to ~0.1 cent precision.
Worked Example — Saxophone Concert F
A tenor sax in concert F4 (sounding F4 = MIDI 65):
- f = 440 × 2^((65 − 69)/12) = 440 × 2^(−4/12) = 440 × 0.7937 = 349.2 Hz
If a tuner reads 350.5 Hz, the cents offset is:
- cents = 1200 × log₂(350.5 / 349.2) = +6.5 cents (very slightly sharp)
Caveats
The MIDI standard does not specify a tuning reference — it only enumerates semitones. A pitch bend message lets a synthesizer render any cent offset from the basic semitone grid, which is essential for microtonal performance. The conversions here assume 12-tone equal temperament; for just intonation or other systems, use cent-ratio conversions instead.