Tuning Frequency Calculator
Calculate
Formula
f = 440 x 2^((n-49)/12) where n is the piano key number, or equivalently f = 440 x 2^(semitones_from_A4 / 12). Wavelength = speed of sound / frequency. MIDI note = 12 x (octave + 1) + note_index.
Frequently Asked Questions
What is equal temperament tuning?
Equal temperament divides the octave into 12 equal semitones. Each semitone has a frequency ratio of 2^(1/12) or approximately 1.05946. This allows instruments to play in any key equally well.
Why is A4 tuned to 440 Hz?
A4 = 440 Hz was adopted as the international standard (ISO 16) in 1955. Some orchestras tune slightly higher (441-443 Hz) for a brighter sound. Historical tuning varied widely from 415 to 466 Hz.