Semitone Frequency Calculator

About this calculator

In equal temperament — the tuning system behind virtually all modern Western instruments — the octave is divided into 12 equal semitones on a logarithmic scale, so any note's frequency can be found from its distance in semitones (n) from the reference pitch A4 = 440 Hz: f = 440 × 2^(n/12). Each semitone step multiplies frequency by the twelfth root of two (about 1.0595), which is why doubling frequency always corresponds to exactly 12 semitones — one full octave.

This formula is the mathematical backbone of every electronic tuner, digital synthesizer, and MIDI system in use today, since MIDI note numbers are just semitone offsets that get converted to frequencies with exactly this equation before being sent to a speaker or synthesizer voice.

Piano tuners and instrument technicians verifying pitch, synth programmers and sound designers building custom scales, and music theory students studying equal temperament all use this relationship to move fluently between note names, semitone offsets, and physical frequency in Hz.