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Musical Note Frequency Calculator

Find any note's frequency in twelve-tone equal temperament from its pitch class and octave, with an adjustable concert-pitch reference (A4 = 440 Hz by default).

Frequency
440 Hz
Semitones from A4
0

How it works

Twelve-tone equal temperament splits every octave into 12 equally-spaced semitones, each a frequency ratio of the twelfth root of two, and pins the whole scale to one reference note — almost universally A4 = 440 Hz today. Any note's frequency follows from how many semitones it sits from that reference: f = referencePitch × 2^(n/12), where n is the signed semitone distance (using scientific pitch notation, where A4 is the A above middle C, C4).

The reference pitch defaults to the modern 440 Hz standard but is a genuine, adjustable input — orchestras and piano tuners sometimes tune slightly sharp, commonly to 442 or 443 Hz, instead. When you change it, this calculator also reports the resulting deviation in cents from standard 440 Hz tuning (1200 × log2(reference ÷ 440)), which is the same for every note since shifting the reference shifts the whole scale by one constant ratio.

Middle C (C4) comes out to about 261.63 Hz and A3, one octave below concert A, comes out to exactly 220 Hz — both widely published reference figures for equal-temperament tuning.

FAQ

Why is A4 the reference note instead of C?

It's a historical convention, not a mathematical necessity — early 20th-century standardization efforts settled on tuning the A above middle C to a fixed frequency (440 Hz became the international standard in 1955), and instrument makers and orchestras have tuned to an 'A' ever since. Any note could serve as the anchor; the formula just needs one fixed point to build the rest of the scale from.

Is 1 cent audible?

Generally no — a well-trained ear can sometimes detect differences as small as 5-6 cents, and the typical threshold for casual listeners is closer to 10-25 cents. A 2 Hz shift in concert pitch (440 to 442 Hz) works out to a little under 8 cents, which is why orchestras can shift concert pitch slightly without most listeners noticing anything is 'off,' even though instruments tuned to different references would clash if played together.

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