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

This calculator uses scientific pitch notation, where middle C is C4. Not every program agrees. Ableton Live, Logic and Cubase all label MIDI 60 as C3, and FL Studio labels it C5, so the same note can carry three different octave numbers on three screens. The MIDI number never moves, which is why it is worth writing down instead of the name. 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 sounding concert F4, which is MIDI 65:

• f = 440 × 2^((65 - 69)/12) = 440 × 2^(-4/12) = 440 × 0.79370 = 349.23 Hz

Now suppose a tuner reads 350.5 Hz on that note:

• cents = 1200 × log₂(350.5 ÷ 349.23) = +6.3 cents, very slightly sharp

Carry the full 349.23 rather than rounding to 349.2 first. The rounded figure gives +6.4, which is close enough for a rehearsal and will not match the calculator above.

Caveats

The MIDI standard does not specify a tuning reference. It only enumerates semitones, which is why the A4 box on this page exists at all. A pitch bend message lets a synthesizer render any cent offset from the basic semitone grid, and that is what makes microtonal performance possible over MIDI at all. The conversions here assume 12-tone equal temperament. For just intonation or any other system, work in cents and ratios instead.