How is a note frequency calculated?

Equal temperament uses f = ref × 2^((n − 69) / 12), where n is the MIDI note number and ref is the A4 reference. With A4 = 440 Hz and MIDI 69, every other note is a fixed ratio away.

Why can I change the A4 reference?

Concert pitch is usually 440 Hz, but many orchestras tune to 441–443 Hz and historical or baroque tuning uses 415 Hz. Adjusting the reference recalculates every note to match.

Is my input uploaded anywhere?

No — the calculation happens entirely in your browser.

Note Frequency Calculator

Find the exact frequency in Hz for any musical note and octave.

Note frequency calculator — any note to hertz

Every musical note has an exact frequency in hertz. This tool uses 12-tone equal temperament and an adjustable A4 reference (concert pitch, usually 440 Hz) to give you the frequency of any note from the lowest bass to the highest harmonic.

It also reports the MIDI note number and the approximate wavelength in air — handy for synth design, tuning and acoustics. All computed in your browser.