How the frequency to note calculator works
In twelve-tone equal temperament each semitone multiplies frequency by the twelfth root of 2, so notes are evenly spaced on a logarithmic scale. A cent is one hundredth of a semitone.
Cents off = (exact note number − nearest note) × 100
Note frequency = 440 × 2(n − 69) ÷ 12
A4 = 440 Hz is the international standard pitch (ISO 16), and MIDI note 69. Some orchestras tune to 442 or 443 Hz; change the reference to match. Octave numbers follow scientific pitch notation, where middle C is C4 (MIDI 60). Most listeners notice detuning of about 5 to 10 cents between two notes played together.
Worked example
A tone at 261.63 Hz is C4 (middle C), MIDI note 60, essentially in tune (0 cents). A guitar string vibrating at 445 Hz reads as A4 and is about +19.6 cents sharp of 440 Hz.
Frequently asked questions
What note is 440 Hz?
A4, the A above middle C.
What frequency is middle C?
About 261.63 Hz with A4 = 440 Hz.
What is a cent in music?
One hundredth of an equal-tempered semitone; an octave has 1,200 cents.
How do I find the note of a frequency?
Calculate 69 + 12 × log₂(f ÷ 440) and round to the nearest whole number; that is the MIDI note.
Updated October 2026. Results are estimates for education, not financial or medical advice. All math runs in your browser; nothing you type is sent anywhere.