Note Frequency Calculator
The frequency of any note in equal temperament at A4 = 440 Hz or your own tuning, the nearest note to a frequency, transposition and the pitch shift from a tempo change.
Result…
How it's calculated
f = A4 × 2^((n − 69) ÷ 12), n = MIDI note number n = 69 + 12 log₂(f ÷ A4) cents = 100 × (n − nearest whole n) transpose s semitones: f × 2^(s ÷ 12) tempo change: shift = 12 log₂(new ÷ old) semitones
In twelve-tone equal temperament every semitone multiplies the frequency by the twelfth root of 2, so one reference note fixes all the others. The MIDI tuning standard numbers the notes so that A4, tuned to 440 Hz, is 69 and middle C is 60; the calculator uses those numbers, so sharps and flats (C# and Db) give the same pitch. It also turns a measured frequency into the nearest note and how many cents sharp or flat it is, transposes by any number of semitones, and shows how far the pitch moves when a recording is sped up or slowed down without time-stretching: the frequency changes by the same ratio as the tempo.
Your numbers, step by step
About the Note Frequency calculator
This note frequency calculator gives the pitch of any note in twelve-tone equal temperament, at the usual A4 = 440 Hz or any tuning you play at, such as 442 Hz for many orchestras or 432 Hz. Type a note like C4, F#3 or Bb5, or a MIDI note number, and you get its frequency, period and the notes a semitone and an octave above. It also works the other way: enter a frequency from a tuner or a spectrum analyser to find the nearest note and how many cents sharp or flat it is. Two more modes transpose a note by any number of semitones and show how far the pitch moves when a recording is sped up or slowed down without time-stretching. The steps use the MIDI numbering (A4 = 69, middle C = 60), so every result can be checked by hand.
How to use it
- Choose what to “Find”: “Note → frequency”, “Frequency → note”, “Transpose” or “Tempo change”.
- Type the “Note”, such as C4 or Eb3, or enter the “Frequency” in Hz.
- To transpose, enter “Transpose by” in semitones; for a tempo change, enter the “Original tempo” and “New tempo” in BPM.
- Set “Tuning: A4 =” if you do not tune to 440 Hz, then read the frequency or note and the cents in the steps.
Worked example
Middle C is MIDI note 60, so at A4 = 440 Hz its frequency is 440 × 2^((60 − 69) ÷ 12) = 261.626 Hz. A string measured at 445 Hz is 69 + 12 × log₂(445 ÷ 440) = 69.1956, so it is A4 and 19.56 cents sharp. Speeding a 120 BPM track up to 126 BPM is a ratio of 1.05, which raises the pitch by 12 × log₂(1.05) = 0.8447 semitones (84.47 cents): A4 moves to 462 Hz, 15.53 cents below A#4/Bb4.
Updated
Questions people ask
How do I calculate the frequency of a note?
Use f = A4 × 2^((n − 69) ÷ 12), where n is the MIDI note number and A4 is your tuning pitch, usually 440 Hz. Each semitone multiplies the frequency by the twelfth root of 2, about 1.0595, and each octave doubles it. The MIDI tuning standard uses the same numbering.
How many cents is a semitone?
100 cents make one equal-tempered semitone and 1,200 make an octave. Cents between two frequencies are 1,200 × log₂(f₂ ÷ f₁).
Is middle C called C4 or C3?
In scientific pitch notation, used here, middle C is C4 at about 261.63 Hz. Some music software and keyboards call the same key C3, so check which convention your tools use.
Why does changing the tempo change the pitch?
Playing a recording faster without time-stretching raises every frequency by the same ratio as the speed, so 5% faster is about 0.84 semitones higher. Time-stretching software can change tempo without changing pitch. To turn a tempo into delay times, use the BPM delay calculator.
Do pianos and other instruments match these frequencies exactly?
Not always. Pianos are often tuned with stretched octaves, and just intonation, historical temperaments and expressive playing move notes by a few cents, so treat these values as the equal-tempered reference. For period and wavelength from any frequency, use the frequency calculator.