Note Frequency Calculator

Equal temperament is the tuning system used in virtually all modern Western music. It divides the octave into 12 equal semitones, where each semitone has a frequency ratio of 2^(1/12), approximately 1.05946. This means each note is about 5.95% higher in frequency than the note below it. The formula f = 440 * 2^(n/12) calculates the frequency of any note, where n is the number of semitones from A4. For example, middle C (C4) is 9 semitones below A4, so n = -9, giving f = 440 * 2^(-9/12) = 261.63 Hz. Before equal temperament, various tuning systems were used, including just intonation, Pythagorean tuning, and meantone temperament. These systems produced purer intervals for certain keys but sounded out of tune in others. Equal temperament sacrifices the purity of individual intervals to allow music in all keys. The reference frequency of 440 Hz for A4 became the international standard in 1955, though some orchestras tune to 441, 442, or even 443 Hz. Historical tuning standards varied widely, with Baroque pitch often at A4 = 415 Hz and classical period instruments tuning around A4 = 430 Hz. The wavelength of a note depends on the speed of sound, approximately 343 meters per second in air at room temperature. Lower notes have longer wavelengths, which is why bass frequencies require larger speakers and travel differently through spaces than treble frequencies.