Note Frequency Calculator
Frequency of any note (A4 = 440 Hz or custom), or note from Hz.
About this tool
Pick a note and octave to see its frequency, MIDI number, period, wavelength and piano key, and play it. Enter any frequency to find the nearest note and how many cents sharp or flat it is. A table lists every note from octave 1 to 7.
How note frequencies are calculated
Western music uses twelve-tone equal temperament: each semitone multiplies the frequency by 2^(1/12), about 1.0595, so twelve semitones (an octave) exactly doubles it. Concert pitch sets A4 to 440 Hz, and any note's frequency is 440 × 2^((n − 69) ÷ 12), where n is its MIDI note number. That makes middle C (C4, MIDI 60) 261.63 Hz, and the piano's range runs from A0 at 27.5 Hz to C8 at 4,186 Hz. Change the reference to match orchestras tuned to 442 Hz, Baroque pitch at 415 Hz, or 432 Hz. Going the other way, the tool finds the nearest note to a frequency and the difference in cents (hundredths of a semitone): 445 Hz is A4, 20 cents sharp. Honest limits: octave numbers use scientific pitch notation, where middle C is C4 (some software labels it C3); real pianos are stretch-tuned slightly away from these exact values. The guitar tuner and the tone generator are related.
Frequently asked questions
What frequency is middle C?
261.63 Hz with A4 = 440 Hz.
What is the formula for note frequency?
f = 440 × 2^((n − 69) / 12), where n is the MIDI note number (A4 = 69).
What is a cent in music?
One hundredth of an equal-tempered semitone; 1,200 cents make an octave.
What frequency is A4 at 432 Hz tuning?
432 Hz by definition; every other note shifts down by about 31.8 cents compared with 440 tuning.
Is my data sent anywhere?
No. Everything is calculated in your browser, and nothing is stored or sent.