Tempo Changer
Load an MP3, WAV or M4A, set the new tempo (or let the BPM calculator set it) and get a time-stretched WAV that keeps the original pitch. Nothing is uploaded.
Tempo % = target BPM ÷ original BPM × 100.
Use the Tempo Changer
Change the Tempo of an Audio File
Runs in your browser — the file is not uploaded. MP3, WAV, M4A, OGG or FLAC (whatever your browser can decode), up to 100 MB and 15 minutes. Output is a 16-bit WAV.
Choose an audio file to start.
Result
Download WAVBPM Tempo Change Calculator
Tempo Settings
BPM math only. To change an audio file, use the tempo changer above — "Use BPM ratio" copies this result into it.
Leave blank to skip duration calculation.
Enter BPM values and click Calculate to see results.
Speed Ratio
—
× playback speed
Speed Change
—
from original BPM
Repitch Shift
—
key lock off
Original Duration
—
Duration Delta
—
—
New Duration
—
Tempo Reference Table
Based on original BPM| Speed | BPM | Change | Duration | Semitones |
|---|
Method, scope, and privacy
Ratio and duration use direct BPM arithmetic. Repitch is an estimate for coupled speed-and-pitch playback; tempo-only processing can preserve pitch. The audio tool keeps pitch with WSOLA (waveform-similarity overlap-add, 46 ms windows) and changes pitch with linear resampling. Quality depends on the material and the size of the change, so no universal artifact-free range is claimed.
Audio is decoded and processed locally in your browser with the Web Audio API. No audio or entered value is uploaded.
Reference: Audacity Change Speed and Pitch manual and Audacity Speed Changer guide.
Quick answer
Tempo % = target BPM ÷ original BPM × 100. To take a 124 BPM track to 128 BPM, time-stretch it to 128 ÷ 124 = 103.23% (+3.23%). With keep pitch on, the key stays the same; with it off (vinyl-style), pitch rises by 12 × log₂(1.0323) = +0.55 semitones. The new length is the old length ÷ 1.0323.
Examples
| BPM change | Speed | Pitch (key lock off) |
|---|---|---|
| 124 → 128 | 103.23% | +0.55 semitones |
| 125 → 130 | 104.00% | +0.68 semitones |
| 140 → 148 | 105.71% | +0.96 semitones |
| 89 → 124 | 139.33% | +5.74 semitones |
| 126 → 75 | 59.52% | −8.98 semitones |
Load a song to change its tempo, or enter two BPMs to get speed %, ratio, pitch shift and the new duration.
Summary
This tempo changer speeds up or slows down an audio file from 50% to 200% directly in your browser. With keep pitch on it time-stretches the audio (WSOLA overlap-add), so the song changes tempo but stays in the same key. With keep pitch off it resamples like a turntable, so pitch moves with speed. Preview the result and download it as a WAV; the file never leaves your device. The BPM calculator converts an original and target tempo into the exact speed percentage, ratio, pitch shift and new duration, and can set the tempo for the audio tool in one click.
How it works
- Choose an audio file (MP3, WAV, M4A, OGG or FLAC — whatever your browser can decode, up to 100 MB and 15 minutes).
- Set the new tempo in percent, or enter the original and target BPM below and click "Use BPM ratio".
- Leave "Keep pitch" on to time-stretch without changing the key, or turn it off for vinyl-style speed and pitch change.
- Click Change Tempo, then preview the result in the player and download the WAV.
- For the math only: speed ratio = target BPM ÷ original BPM, new duration = original duration ÷ ratio.
- The repitch estimate uses 12 × log₂(ratio) semitones and applies only when key lock or pitch correction is off.
Use cases
- DJs matching a track to the set BPM before mixing.
- Producers time-stretching stems to a project tempo.
- Dance instructors finding a safe stretch percentage for class choreography.
- Runners calculating what BPM a playlist will hit at a given speed bump.
- Music students analyzing how tempo shift affects feel and groove.
- Podcasters adjusting speech-rate audio files to target durations.
- Fitness coaches syncing workout music to target heart-rate cadence.
- Game developers tuning adaptive music loops to match scene pacing.