About this tool
Relate playback speed to pitch three ways: find the semitone and cent shift caused by a speed change, find the speed needed for a given semitone transposition, or read the resulting BPM and frequency. It runs locally in your browser with no uploads.
Speed and pitch are linked by a single ratio. From a speed percentage, ratio = speed ÷ 100, then semitones = 12 × log₂(ratio) and cents = 1200 × log₂(ratio). Going the other way, a semitone shift gives ratio = 2^(semitones ÷ 12) and speed % = ratio × 100 — so +12 semitones doubles the speed to 200%, and −12 halves it to 50%. Any original tempo and frequency you supply are simply multiplied by the ratio: new BPM = BPM × ratio and new frequency = frequency × ratio.
This models classic varispeed behaviour, where changing playback rate shifts pitch and tempo together (as on tape or a naive sampler). Modern time-stretch or pitch-shift plug-ins can change one without the other; use those numbers as your target, and this tool tells you the ratio, semitones, cents, tempo and pitch involved.