Note Frequencies

To calculating the frequency of a given note:

f = f_0 \cdot 2^{\left( \frac{c}{1200} \right)}

Where f is the frequency we're after, f0 is the reference frequency, and c is the pitch shift in cents. 100 cents are a semitone and 1200 cents are an octave. Doubling the frequency of a note puts it up an octave and halving the frequency of a note puts it down an octave.

The reference note to use is A-4 (sometimes called "Concert A"), which in the Equal Tempered Scale is 440Hz. "Middle C" is C-4. Some sources claim that its frequency is 256Hz, probably because 256 is a power of two so it's easier to shift up and down octaves, but its real value is closer to 262Hz.


The fourth and fifth octaves:

NoteFrequency (Hz) NoteFrequency (Hz)
C-4261.63 C-5523.25
C#4277.18 C#5554.37
D-4293.66 D-5587.33
D#4311.13 D#5622.25
E-4329.63 E-5659.26
F-4349.23 F-5698.46
F#4369.99 F#5739.99
G-4392.00 G-5783.99
G#4415.30 G#5830.61
A-4440.00 A-5880.00
A#4466.16 A#5932.33
B-4493.88 B-5987.77

Notice that musical octaves start with a C, not an A.

A semitone on a piano is the next key along, including the sharps (the ebonies.) To find notes in other frequencies either double or halve the frequencies in the table above, depending on whether you're going up or down an octave, respectively.


One fret on a guitar string is one semitone. Here's the classical tuning for a six-string guitar:

NoteFrequency (Hz)
E-2 82.41

For a bass guitar:

NoteFrequency (Hz)

See also

Hz to note converter (PERL script)
“Concert A” Pitch Since 1511

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