Free local tool

Frequency to Musical Note Calculator

Convert frequency, MIDI note number, nearest 12-TET note, and cents deviation using an explicit A4 reference.

Private by design: inputs and local files stay in this browser tab. The tool sends no input to a server and stores nothing after the page closes.

JavaScript is required for the interactive tool.

Method and limits

Uses 12-tone equal temperament with default A4 = 440 Hz and an allowed 400-500 Hz reference. MIDI 60 = C4 and MIDI 69 = A4; sharp spellings are used. Frequency mode reports out-of-MIDI-range results honestly. No audio, microphone, MIDI parsing, playback, or device access occurs.