Tempo Change Calculator
Speed Up the Tempo, Shrink the Runtime
Tempo and duration move in inverse proportion: double the BPM and a passage plays in half the time, at the same pitch and content. DJs, remixers, and editors lean on this relationship constantly — nudging a track's tempo to match a set, or timing a cue to a fixed video length, without recalculating every section by hand. This calculator applies the inverse relationship directly to a known duration and tempo change.
The Formula
Because the ratio is Original BPM over New BPM, raising the tempo (a larger New BPM) always shrinks the duration, and lowering it always stretches the duration — the same relationship time-stretching plugins use internally when a "tempo" knob is adjusted without engaging pitch-correction.
Where This Calculation Matters
- DJ beatmatching — predicting how much a track will shrink or stretch when nudged to match the tempo of the next song in a set.
- Remix and edit work — calculating a track's new runtime after a tempo change, before committing to the time-stretch in a DAW.
- Sync to picture — adjusting a cue's tempo to make a piece of music fit an exact video or scene length.
- Playlist and set timing — estimating total set length changes when several tracks are tempo-matched to a target BPM.
| New tempo | New duration | Tempo change |
|---|---|---|
| 120 BPM | 256.0 s (4:16) | −6.25% |
| 124 BPM | 247.74 s (4:07.7) | −3.12% |
| 132 BPM | 232.73 s (3:52.7) | +3.12% |
| 140 BPM | 219.43 s (3:39.4) | +9.38% |
Computed from New Duration = Original Duration × (Original BPM / New BPM) for a 240-second track starting at 128 BPM.
How to Use This Calculator
- Enter the original tempo in BPM.
- Enter the new tempo you're changing to, in BPM.
- Enter the original duration in seconds.
- Select Calculate to get the new duration and the percentage tempo change.
Related Calculations
Work from bar counts instead of a known duration with the Song Length Calculator, or convert the resulting tempo into a click interval with the Metronome Calculator.