Frequency to Note Converter
Convert between Hz, musical notes and semitones using equal temperament tuning.
This free converter translates between frequency in Hertz and musical notes using 12-tone equal temperament, the tuning system used by virtually all modern instruments. Enter a frequency to instantly see its nearest note name, octave and how many cents sharp or flat it is, or pick a note to get its exact frequency — all based on a customizable reference pitch (A4, defaulting to the standard 440 Hz).
This is useful for tuning instruments, understanding synthesizer oscillator frequencies, checking how far a recorded pitch drifts from standard tuning, or simply exploring the relationship between frequency and musical pitch. The calculator also shows the semitone offset from the reference A4, which is handy when working with pitch-shifting or transposition in cents and semitones.
Frequently Asked Questions
What is equal temperament?
12-tone equal temperament (12-TET) is the standard tuning system that divides an octave into 12 equal semitones, so each semitone is a frequency ratio of the 12th root of 2 (≈1.0595) from the previous one.
What is A4 and why is it 440 Hz?
A4 is the A above middle C, and 440 Hz has been the international standard reference pitch since 1955 (ISO 16). All other note frequencies in this calculator are derived relative to this reference.
How do I convert a frequency to a note name?
The calculator computes the number of semitones the frequency is from A4 using the formula 12 × log₂(f ÷ 440), rounds to the nearest semitone to find the note, and shows the remaining difference in cents.
What are cents in music?
A cent is 1/100th of a semitone. Cents describe how far a frequency deviates from the "perfect" pitch of the nearest note — useful for describing subtle tuning differences that are smaller than a semitone.
How do I find the frequency of a specific note, like C4?
Select the note and octave in the calculator, and it computes the frequency using f = 440 × 2^((n-69)/12), where n is the MIDI note number corresponding to that note and octave.
What octave is middle C?
Middle C is typically labeled C4 in scientific pitch notation, corresponding to a frequency of about 261.63 Hz in standard 440 Hz tuning.
Can I change the reference pitch from 440 Hz?
Yes. Some orchestras and historical tuning systems use a slightly different reference (such as 442 Hz or 415 Hz for baroque pitch) — you can adjust the A4 reference field and all conversions update accordingly.
What is a semitone offset?
The semitone offset shows how many equal-tempered semitones a frequency is above or below the reference A4 pitch — a positive number means higher in pitch, negative means lower.
Why might a recorded or synthesized frequency not match a note exactly?
Real-world audio, analog synthesizers, and slightly out-of-tune instruments rarely produce frequencies that land exactly on a 12-TET note — the cents value shows precisely how far off it is.
Is 12-TET the only tuning system?
No — historical and some non-Western music traditions use different tuning systems (like just intonation or various meantone temperaments), but 12-TET is the near-universal standard for modern Western instruments and this calculator.