Note Name to Frequency Calculator
Every note on a MIDI keyboard has a number, and every number maps to a precise frequency through equal temperament. MIDI 69 is A4, the reference pitch, and each step of one is a semitone above or below. This calculator takes a MIDI note number and a reference A4 frequency, then returns the note's frequency in hertz, its name and octave in scientific pitch notation, and its distance from A4 in semitones. Producers, synth programmers, and instrument builders use it to look up exact frequencies, set oscillators, and check that a device is tuned to the right standard.
MIDI to frequency formula
Frequency = reference A4 * 2^((MIDI number - 69) / 12)
Semitones from A4 = MIDI number - 69
Octave (scientific) = floor(MIDI number / 12) - 1
Period in ms = 1000 / frequency
MIDI 69 is A4 and MIDI 60 is middle C (C4). The note name comes from the MIDI number modulo 12; the period is the time for one cycle of the waveform.
MIDI and pitch context
- MIDI 69 = A4 = 440 Hz at standard tuning; MIDI 60 = C4 = about 261.63 Hz.
- Each MIDI step is one semitone; twelve steps is an octave, doubling the frequency.
- Scientific pitch notation increments the octave number at each C.
- Change the reference A4 to match orchestral (442 to 443 Hz) or baroque (415 Hz) tuning.
- The valid MIDI range is 0 (C-1) to 127 (G9).
Note to frequency: frequently asked questions
How does a MIDI note number map to a frequency?
MIDI numbers notes from 0 to 127, with middle A (A4) at number 69. The frequency is the reference A4 frequency times two raised to the note number minus 69, all over twelve. With A4 at 440 Hz, note 69 is 440 Hz and each step of one is a semitone.
What note is MIDI number 60?
MIDI 60 is middle C, written C4 in scientific pitch notation. Its frequency with A4 at 440 Hz is about 261.63 Hz. The calculator names the note and octave for any MIDI number you enter, from 0 (C-1) up to 127 (G9).
Why can I change the reference A4?
A4 at 440 Hz is the international standard, but orchestras often tune to 442 or 443 Hz and baroque ensembles to 415 Hz. Changing the reference shifts every note by the same ratio, so the tool can match any tuning standard you need.
What is scientific pitch notation?
Scientific pitch notation names a note by its letter and an octave number, where the octave increments at each C. Middle C is C4 and the A above it is A4. MIDI octave numbering aligns so that MIDI 60 is C4 in this widely used convention.
Does this use equal temperament?
Yes. Each semitone is the twelfth root of two, the equal-tempered ratio used by virtually all modern instruments and MIDI devices. For just intonation or other tuning systems the ratios differ, but for standard MIDI playback equal temperament is correct.
Official sources
- UNSW School of Physics: Note names, MIDI numbers and frequencies.
- MIDI Association: MIDI 1.0 note number specification.
Reviewed by the CalculatorHub team, edited by James Graham, 17 June 2026. See our methodology.