Note & Frequency Calculator
The frequency in hertz of every musical note from C0 to B8, with an adjustable A 4 reference. Convert a note to its frequency, or a frequency to the nearest note plus its cents offset. Pure equal-temperament math — no microphone, no signup.
Note → Frequency
Frequency → Note
Tap any value to copy it to your clipboard.
How note frequencies are calculated
Western music uses twelve-tone equal temperament: the octave is split into twelve equal steps, and each step multiplies the frequency by the twelfth root of two (about 1.05946). Pin one note to a known frequency and every other note follows. The anchor is A 4 = 440 Hz, concert pitch. Using MIDI note numbers (A4 = 69), the frequency of any note n is:
f(n) = 440 × 2(n − 69) / 12
That is why an octave doubles the frequency: A3 is 220 Hz, A4 is 440 Hz, A5 is 880 Hz. Middle C (C4) lands on about 261.63 Hz.
Frequency to note & cents
Going the other way, a cent is one hundredth of a semitone, so 100 cents is one half-step and 1200 cents is an octave. Type any frequency above and the calculator finds the closest note, then tells you how many cents flat or sharp it sits — exactly what you need to check whether a sample, synth oscillator or recording is in tune.
432 Hz, 442 Hz and other references
Not everyone tunes to 440. Some prefer 432 Hz for a slightly darker, lower pitch; many orchestras tune sharp to 442 or 443 Hz for brilliance. Change the A 4 reference at the top and the entire chart and both converters retune instantly. Once you know your note, open the Chord & Scale Explorer to build a progression around it, or the Delay & Reverb Calculator to lock your effects to the tempo.