Musical Note to Frequency Calculator

Each note maps to a MIDI number n = 12 times (octave + 1) plus its semitone index. The frequency is f = A4 times 2 to the power (n minus 69) over 12, where A4 is MIDI 69 and the tuning reference.

Equal temperament splits the octave into twelve identical steps, so each semitone is the twelfth root of two, about 1.05946, apart in frequency. It is the tuning used by pianos and most modern instruments because every key sounds equally in tune.

440 Hz is the modern standard, but some musicians prefer 432 Hz, and baroque ensembles often tune to 415 Hz. Set the A4 box and every note or frequency is recalculated against the new reference.

Cents measure how far a frequency sits from the nearest equal-tempered note, with 100 cents to a semitone. A reading of +39 cents means the pitch is about two fifths of a semitone sharp of the note shown.

Middle C is C4 in scientific pitch notation, at 261.63 Hz when A4 is 440 Hz. The A directly above it is A4 at 440 Hz, and the C an octave up is C5 at 523.25 Hz.

The Note to Hz dropdown lists notes with sharps, but the engine also understands flat spellings such as Db, Eb, Gb, Ab and Bb, treating each as the same pitch as its enharmonic sharp.

The octave selector runs from 0 to 8, spanning C0 at about 16.35 Hz up to B8. In Hz to note mode you can paste any positive frequency and it will report the nearest note even outside that range.

The cents figure is computed to six decimal places, so 450 Hz reads as +38.905773 cents rather than a rounded +39. That precision helps when checking the tuning of a recorded or measured pitch.

No. Both conversions run entirely in your browser, so the notes and frequencies you enter stay on your device.