Note Frequency Calculator
Find the exact frequency of any musical note in any octave, with its MIDI number, wavelength and period. Retune the A4 reference to 432 Hz or any value. Runs in your browser.
Frequency
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Show the math
Equal temperament splits the octave into twelve equal semitones. Each note's pitch is found from its distance in semitones from A4:
frequency = A4 × 2^((MIDI − 69) ÷ 12)
The default A4 is 440 Hz; change it to 432 Hz or any other reference to retune the whole scale. Wavelength uses a speed of sound of 343 m/s.
Everything is calculated in your browser.
What this does
A note frequency calculator finds the exact frequency of any musical note in any octave, with its MIDI number, wavelength, and period, and lets you retune the A4 reference.
How to use it
- Choose the note and octave.
- Set the A4 reference (440 or 432 Hz).
- Read the frequency.
- See the MIDI number and wavelength.
How it works
Equal temperament splits the octave into twelve equal semitones from the A4 reference. Wavelength = speed of sound ÷ frequency, using 343 m/s for air at ~20 °C.
f = A4 × 2^((MIDI − 69) ÷ 12)
Understanding your result
These frequencies assume equal temperament tuned to your A4 reference, so changing the reference (say to 432 Hz) shifts every note proportionally. Use the exact hertz values to tune synths, set filter or EQ points to a musical pitch, or check an instrument, and note the wavelength figure depends on the speed of sound, which varies with air temperature.
Example
A4 = 440 Hz makes middle C (C4) about 261.6 Hz.
Sources & methodology
Last updated .
Frequently asked questions
How is the frequency worked out?
Equal temperament splits the octave into twelve equal semitones, so frequency = A4 × 2^((MIDI − 69) ÷ 12). A4 defaults to 440 Hz.
Can I use a different tuning reference?
Yes, change the A4 value to 432 Hz or any other reference and the whole scale retunes around it.
How is the wavelength found?
Wavelength = speed of sound ÷ frequency, using 343 m/s for air at about 20 °C. It is shown in centimetres alongside the period in milliseconds.
Is anything stored?
No. Everything is calculated locally in your browser.
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