🎵 Note Frequency Calculator
Convert any note to its frequency in hertz (and MIDI number), or find the nearest note for a frequency — with an adjustable reference pitch.
Frequency
440 Hz
MIDI note
69
A4
Equal temperament: f = A4 × 2^((n − 69)⁄12), with A4 = 440 Hz (ISO 16) and middle C = C4 = MIDI 60. Change the reference for A=432 or historical tunings. 100 cents = one semitone. 🔒 In your browser.
How the note frequency calculator works
In equal temperament, each note's frequency is f = A4 × 2^((n − 69)⁄12), where n is the MIDI note number and A4 (MIDI 69) is the reference, standardised at 440 Hz. The tool computes the frequency for any note and octave, or works backwards from a frequency to the nearest note and how many cents sharp or flat it is. Change the reference to tune to A=432 or older pitch standards.
Middle C is C4 = MIDI 60 (scientific pitch notation). Each octave doubles the frequency, and there are 100 cents to a semitone. The 440 Hz standard is ISO 16; some orchestras and genres use 442, 443 or the alternative 432 Hz.
Frequently asked questions
What is the frequency of A4?
A4 (the A above middle C) is 440 Hz by the modern standard (ISO 16). Every other note is derived from it: f = 440 × 2^((MIDI − 69)⁄12).
How do I convert a note to a frequency?
Use equal temperament: f = 440 × 2^((n − 69)⁄12), where n is the note's MIDI number. Middle C (C4, MIDI 60) is about 261.63 Hz; A5 is 880 Hz (an octave above A4). The tool does it for any note.
What is A=432 tuning?
An alternative reference pitch of 432 Hz for A4 instead of 440, favoured by some for its supposed warmer sound. Set the reference to 432 and the tool retunes every note accordingly.
What are cents in music?
A cent is 1⁄100 of a semitone — 1,200 cents to an octave. They measure fine tuning differences: a note 10 cents sharp is slightly, but audibly, higher than in tune. The tool shows how many cents a frequency is off the nearest note.
What is a MIDI note number?
A number from 0 to 127 identifying a pitch, where 69 is A4 (440 Hz) and 60 is middle C. MIDI numbers make it easy to compute frequencies and transpose by simple addition.