How to find the BPM and key of a song
- Choose an MP3, WAV or M4A file. The analysis starts right away.
- Read the BPM and key. If the song feels twice as fast or slow, use the half or double time number.
- No file? Use Tap tempo: tap along on every beat for a few bars.
How BPM detection works
First the song is cut into slices about 12 milliseconds long, and for each slice we measure how much new sound arrives across all frequencies. Drum hits, plucks and chord changes make sharp peaks, and steady sounds make almost none. That gives an “onset” curve that pulses with the rhythm.
Then we compare that curve with delayed copies of itself, which is called autocorrelation. When the delay matches the length of one beat, the peaks line up and the match is strongest. A beat that repeats every 0.5 seconds is 120 BPM. We check the match at two, three and four beats as well, keep the answer between 60 and 200 BPM that fits best, and then fine tune it across many beats so a 120 BPM track reads 120, not 119.4.
How key detection works
For the key, the song is split into its frequencies with a Fourier transform, and the energy of every note is folded into the 12 pitch classes, so every C counts towards C whatever its octave. That gives a profile of which notes the song uses most. We compare it with the Krumhansl-Kessler profiles, which come from music psychology studies of how strongly each note belongs in each of the 24 major and minor keys, and the closest match is the key.
The usual mix-up is between a major key and its relative minor, like C major and A minor, because they share every note. The result card shows the relative key so you can pick the one that matches the mood: brighter means major, darker means minor.
Common BPMs by genre
| Genre | Typical BPM |
|---|---|
| Hip-hop and boom bap | 85 to 95 |
| Lo-fi hip-hop | 70 to 90 |
| Trap | 130 to 150 (felt at 65 to 75) |
| Drill (UK and NY) | 140 to 145 |
| R&B | 60 to 80 |
| Afrobeats | 95 to 115 |
| Reggaeton | 88 to 100 |
| Pop | 100 to 130 |
| House | 120 to 128 |
| Techno | 125 to 140 |
| Dubstep | 140 (felt at 70) |
| Drum and bass | 170 to 176 |
These are starting points, not rules. Plenty of hits sit outside them, and a lot of modern rap moves between half time and double time in the same song. Need a song at a different tempo? Use the BPM changer, and the pitch shifter to move it to a different key.
FAQ
How accurate is the BPM finder?
For music with a steady beat, like most hip-hop, pop and electronic tracks, it’s usually within a tenth of a BPM. Songs played live without a click, or with tempo changes, get an average, so tap along to double check those.
Why does it say 70 BPM when my beat is 140?
Both are right in a way. Trap, drill and dubstep are often felt at half time, so the same beat can be counted at 70 or 140. We pick the reading between 60 and 200 BPM that fits the strongest pulse and show the half and double time numbers under it.
What does the Camelot number mean?
The Camelot wheel gives each key a code from 1A to 12B so DJs can mix in key without music theory. Keys with the same number, or a number one step away, blend well. 8B is C major and 8A is A minor, for example.
Can it find the key of a beat or a drum loop?
It finds the key of anything with notes in it: melodies, chords, 808s and vocals. A loop with only drums doesn’t really have a key, so the result won’t mean much. Major keys and their relative minors share the same notes, so if the result feels wrong, try the relative key we show.
Is my song uploaded?
No. The analysis runs in your browser, so your file never leaves your device. It’s free with no sign-up.
How does tap tempo work?
Tap the button in time with the music, on every beat. After two taps you get a BPM, and it gets steadier the longer you tap, using the average gap between your last few taps. Pause for two seconds to start over.