Musical note frequencies
Convert a musical note to frequency (Hz) and a frequency to a note, with the difference in cents, the MIDI number and the wavelength, using A = 440 Hz or another reference, such as 432 or 442 Hz.
How to useNote to Hz and Hz to note
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Musical note frequencies: what it is for
Convert any note to frequency with the equal temperament formula, f = 440 × 2^((n − 69) / 12), and go the other way: type a frequency in hertz and see the nearest note and how many cents it is above or below. You can change the A4 reference to 432, 442 or 443 Hz, and a table shows the frequency of every note from octave 0 to 8. The MIDI number, period and wavelength in air also appear.
The sound is generated in your browser with the Web Audio API: nothing is recorded or sent to a server.
How to use
- Choose the note and octave.
- Adjust the reference A if needed.
- Type a frequency to find the note.
When to use it
- Programming synthesizers and audio plugins.
- Physics and acoustics projects.
- Checking the tuning of instruments and recordings.
Frequently asked questions
What is the formula for a note's frequency?
In equal temperament, each half step multiplies the frequency by the twelfth root of 2 (about 1.0595). With A4 at 440 Hz, the frequency is 440 × 2^((n − 69) / 12), where n is the note's MIDI number. Middle C (C4) is about 261.63 Hz.
What are cents?
They divide the half step into 100 equal parts. A note 10 cents above is slightly sharp; past about 50 cents, it is already closer to the next half step.
Why is there 432 Hz tuning?
440 Hz has been the international standard since the 20th century, but some orchestras tune to 442 or 443 Hz and some people prefer 432 Hz. Changing the reference shifts every note by the same proportion.
Is it really free?
Yes, 100% free. No sign-up, no subscription and no usage limits. All Tools123 tools are free and run right in your browser.