Start with the counter-intuitive part: forcing a song to exactly 180 BPM is usually the wrong move. Most "why does my running music sound muffled/metallic/warbly" complaints come from that one decision — not from the song, and not from the tool.
1. You don't actually need 180 BPM. You need an integer relationship.
When you run, you want your footstrike to land on the beat. If your cadence is 180 steps per minute, a track works as long as every step lands on a beat — and the track's own tempo can be:
| Song BPM | Steps per beat | What it feels like |
|---|---|---|
| 180 | 1 step per beat | Every single step on a beat — busiest feel |
| 90 | 2 steps per beat | One beat per stride cycle — more relaxed |
| 60 | 3 steps per beat | One beat every three steps — good for slow tracks |
| 45 | 4 steps per beat | One beat every four steps |
| 36 | 5 steps per beat | One beat every five steps |
In other words, an 80 BPM track doesn't need to be dragged up to 180. Snap it to 90 or 60 and it still lands perfectly on a 180 spm cadence. This matters enormously, because it's the single biggest factor in how the result sounds.
2. Why "change as little as possible" wins
There are two ways to speed up a song:
- Change the pitch (resampling): like fast-forwarding a tape. Tempo and pitch rise together and vocals turn into chipmunks.
- Keep the pitch (time-stretching): the tempo moves, the key stays put. This is what the editor does.
The core algorithm behind time-stretching is SOLA (synchronous overlap-add): the audio is chopped into segments of roughly 23 milliseconds and re-joined at a new spacing. To avoid an audible click at each seam, the algorithm searches a small neighbourhood for the most similar waveform before aligning. That search window is only about 5.8 ms wide.
That gives us the whole rule:
The closer the tempo multiplier is to 1, the more candidate alignments exist and the smoother the seams. The further it drifts from 1, the more often the search window comes up empty — and you hear it as stuttering drums, smeared vocal attacks and a metallic sheen.
The multiplier here is target BPM ÷ original BPM. A multiplier of 1.15 means the track runs 15% faster. A multiplier of 3.46 means 246% faster, and the processing artefacts will be obvious.
3. The three modes, and how to choose
The editor offers three approaches. They differ only in how much gets changed:
- Nearest cadence (approximate): snap the track to whichever divisor of 180 — 180, 90, 60, 45, 36, 30 — gives a multiplier closest to 1. Smallest change.
- Exact cadence: force the track to 180 BPM, one step per beat. Largest change.
- Beats only: leave the song's tempo untouched and overlay footsteps or hand drums at 180 per minute, letting the percussion carry the rhythm.
The third option is underrated. If your favourite track sits around 128 BPM, both tempo changes will audibly distort it — and adding drum hits alone is usually the best-sounding answer.
4. Tempo multiplier chart
The table below shows where the approximate mode actually lands. Note the rule it uses: multiplier closest to 1, not smallest BPM difference — which is why several rows won't match your intuition.
| Original BPM | Approximate lands on | Approximate multiplier | Exact multiplier |
|---|---|---|---|
| 52 | 60 | ×1.15 | ×3.46 |
| 60 | 60 | ×1.00 (untouched) | ×3.00 |
| 75 | 90 | ×1.20 | ×2.40 |
| 90 | 90 | ×1.00 (untouched) | ×2.00 |
| 100 | 90 | ×0.90 | ×1.80 |
| 120 | 90 | ×0.75 | ×1.50 |
| 128 | 180 | ×1.41 | ×1.41 |
| 140 | 180 | ×1.29 | ×1.29 |
| 150 | 180 | ×1.20 | ×1.20 |
| 160 | 180 | ×1.13 | ×1.13 |
A few counter-intuitive reads from this table:
- 60 and 90 BPM tracks need no tempo change at all. They're already integer divisors of 180 — just add the beat overlay.
- Never use exact mode on a 52 BPM ballad. ×3.46 will mangle the vocals completely. Approximate mode takes it to 60, only 15% faster, and it's nearly undetectable.
- A 120 BPM track will be slowed to 90 in approximate mode (×0.75), which can sound slightly dulled. If it feels muddy, try exact mode (×1.50) instead — it will sound brighter, not worse.
- Above 128 BPM both modes agree. That's a moderate change and entirely acceptable.
5. The three steps
- Import the song: just drop the file in — BPM is detected automatically. Detection is very reliable on electronic and dance music; live recordings, classical pieces and free-tempo tracks can be off, in which case trust your ears and set it manually.
- Set the target cadence: 180 by default; anything from 50 to 200 works. Don't treat 180 as gospel — see the next section.
- Pick a mode → pick a beat → hit adjust: newcomers should start with nearest cadence. If the result sounds dull, try exact cadence. If neither satisfies you, use beats only.
When you're happy, open the export page to merge several tracks into a single MP3 you can play start to finish on a run.
6. About that 180 number
The 180 figure is usually traced back to observations of elite distance runners at the 1984 Olympic Games, where most were clocked at roughly 180 steps per minute. Two caveats:
- That's an observation, not a training standard. It describes what high-level runners happen to do, not what everyone should aim for.
- Height, leg length and pace all shift your natural cadence. Taller runners and slower paces tend towards lower cadences, and forcing 180 can disrupt your breathing rhythm.
The more useful approach: measure your own natural cadence first, then set your target. Run for one minute, count your right-foot strikes, and double it. Nudge up from there — say +5 spm — rather than jumping straight to 180.
One numeric curiosity that helps explain the table above: 180 steps per minute is three steps per second, which is 90 full stride cycles per minute. That's exactly why a 90 BPM track fits so naturally — one beat per stride cycle.
7. Six mistakes worth avoiding
- Assuming you must hit 180 BPM. As shown above, 90 or 60 BPM aligns just as precisely and sounds better.
- Ignoring the multiplier. Check it before choosing a mode. Anything above ×1.3 deserves the expectation of some quality loss.
- Cranking the beat overlay too loud. The percussion is there to carry the rhythm, not to be the track. The default level is usually right; push it up and it buries the vocals.
- Mixing target cadences before merging. The export page concatenates in list order, so if some tracks were set to 180 and others to 170, your rhythm will drift mid-run.
- Dragging slow songs up to speed. For anything under 60 BPM, beats only beats a 3× speed-up every time.
- Worrying about audio privacy. Everything runs locally in your browser — your audio files are never uploaded to any server. Close the page when you're done and nothing is retained.
8. FAQ
Why does the result sound a bit smeared? Almost always a high multiplier. Switch to nearest cadence, or pick a track whose tempo is closer to 90 or 180 to begin with.
The detected BPM doesn't match what I know it to be. Automatic detection is most accurate on percussion-heavy electronic music. Vocal-led or free-tempo material drifts more easily — set it manually by ear.
Can I stack more than one beat overlay on a track? One overlay per pass. For a compound rhythm, run the track twice with different beats, export both, then merge them on the export page.
Does it work on a phone? Yes. Processing happens in the browser, and the major iOS and Android browsers all support it. No app install required.
Pick your favourite track and run it through nearest cadence once, then compare against exact cadence. The difference is immediately audible.