Note ↔ Frequency Converter

Convert between musical note names, frequencies (Hz), and MIDI numbers. Tune the reference pitch, detect the closest note from any Hz value, and play each pitch in your browser.

Inputs

Frequency (Hz)

Note name (e.g. A4, C#5, Db3)

MIDI number (0–127)

A4 reference (Hz)

Wave:

Result

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Note

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Frequency

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MIDI

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Cents Offset

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Period (ms)

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Wavelength (m)

Piano (C3 – B5)

Octave Reference (A0 – C8)

Octave	C	C#/Db	D	D#/Eb	E	F	F#/Gb	G	G#/Ab	A	A#/Bb	B

About Equal Temperament

In 12-tone equal temperament, every semitone is a fixed ratio of 2^1/12 (≈1.0595). MIDI number 69 is A4, fixed by the international reference at 440 Hz. Frequency from MIDI is f = A4 × 2^{(n − 69) / 12}. One cent is 1/100 of a semitone, so the distance in cents between two frequencies is 1200 × log₂(f2 / f1). Change the A4 reference above to try baroque (415 Hz), classical (430 Hz), or other tunings.