BPM Finder · Tempo Finder · BPM Detector
BPM Finder
Drop a song and get its BPM, beat grid and key in seconds — detected on your device, free, with a click track to check the result.
How the BPM finder works
There is no server behind this page. The file is decoded and analysed by the same tab you are reading this in, using nothing but the Web Audio API and a small amount of DSP. That is what makes a real BPM detector possible for free, with no upload queue and no account.
1 · Decode on your device
The browser turns the file into raw PCM samples. Nothing is uploaded, which is why the tool is free and instant.
2 · Find the onsets
Every drum hit, pluck and chord attack shows up as a jump in energy. The analyser builds an onset curve from those jumps.
3 · Measure the repeat
The curve repeats at the beat period. Autocorrelation finds that period, a musical tempo prior resolves half/double time, and the result is converted to BPM.
Upload, tap, or look it up?
| Approach | Best for | Where it breaks |
|---|---|---|
| Upload a file | Whole-track tempo, beat grid, key | Needs the file; DRM-protected audio cannot be read |
| Tap the beat | Any audio you can hear — streams, vinyl, a live band | Human error on fast or drifting tempos |
| Song database | Huge catalogues, key + BPM + release data | Misses unreleased, private or local files |
This page covers the first two: a file gives you the beat grid, and when you only have the audio playing, use the tap BPM counter instead — both pages measure the same thing, one from a file and one from your taps.
What to do with the number
Key reference: relative minor and I–V–vi–IV
Once you have the key, the relative minor tells you which scale to solo or write in, and the I–V–vi–IV progression is the backbone of a very large share of pop songs — a useful starting point for playing along.
| Key | Relative minor | I – V – vi – IV |
|---|---|---|
| C | Am | C – G – Am – F |
| C# / Db | A#m / Bbm | Db – Ab – Bbm – Gb |
| D | Bm | D – A – Bm – G |
| D# / Eb | Cm | Eb – Bb – Cm – Ab |
| E | C#m | E – B – C#m – A |
| F | Dm | F – C – Dm – Bb |
| F# / Gb | D#m / Ebm | Gb – Db – Ebm – Cb |
| G | Em | G – D – Em – C |
| G# / Ab | Fm | Ab – Eb – Fm – Db |
| A | F#m | A – E – F#m – D |
| A# / Bb | Gm | Bb – F – Gm – Eb |
| B | G#m | B – F# – G#m – E |
Tuning up before you play along? The pitch detector reads your instrument in cents, and the tone generator gives you a reference pitch. If the beat seems to favour one ear, run the headphone test.