MIDI Note to Frequency Calculator

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

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:

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.