How the BPM finder works
BPM means beats per minute: how many times per minute you would tap your foot to the song. The finder works it out in three steps, all inside your browser:
- Onsets. The audio is cut into short slices, and each slice is compared with the one before it. Sudden jumps in energy across the spectrum mark where notes and drum hits start.
- Tempo. The onset pattern is compared with shifted copies of itself. The shift at which it lines up best is the beat period, which gives the BPM.
- Beats. A beat tracker then places each individual beat, following the song when the drummer pushes or drags a little. Those are the clicks you hear on playback.
The same beat tracker drives our lyric video maker, where the cuts between lyric lines snap to the beat. If you want a lyric video for the song you just analysed, use the button above: the song goes straight into the editor, still without being uploaded.
Half time, double time and why both can be right
A song at 140 BPM can feel like 70 if the snare lands on every other beat, and a slow ballad at 70 can be counted at 140 in eighth notes. Neither is a mistake; they are two ways of counting the same pulse. The result card shows both readings. Pick the one your DJ software, click track or video editor expects, or tap along and see which one your foot agrees with.
BPM to seconds
One beat lasts 60 ÷ BPM seconds. That is handy when you edit video to music: at 120 BPM a beat is exactly half a second, so a cut every 15 frames at 30 fps stays on the beat.
| BPM | One beat | One 4/4 bar | Frames per beat at 30 fps |
|---|---|---|---|
| 60 | 1.000 s | 4.00 s | 30.0 |
| 70 | 0.857 s | 3.43 s | 25.7 |
| 80 | 0.750 s | 3.00 s | 22.5 |
| 90 | 0.667 s | 2.67 s | 20.0 |
| 100 | 0.600 s | 2.40 s | 18.0 |
| 110 | 0.545 s | 2.18 s | 16.4 |
| 120 | 0.500 s | 2.00 s | 15.0 |
| 128 | 0.469 s | 1.88 s | 14.1 |
| 140 | 0.429 s | 1.71 s | 12.9 |
| 150 | 0.400 s | 1.60 s | 12.0 |
| 160 | 0.375 s | 1.50 s | 11.3 |
| 174 | 0.345 s | 1.38 s | 10.3 |
What to do with a song’s BPM
- DJing and mixing: match the tempos of two tracks before you blend them.
- Video editing: place cuts on beats or bars so the edit feels locked to the music.
- Practice: set a metronome to the song’s tempo, or slow it down and work back up.
- Playlists: group songs of similar tempo for running, dance classes or a steady mood.
- Harmony: tempo is half of what makes two songs mix well; the other half is key. Our key finder works the same way, in the browser.