BPM Detector

How it works

1. Choose an audio file.
2. Wait for the analysis to finish.
3. Read the BPM and confidence; check the half and double values if it looks off.

How the tempo is estimated

The file is decoded, mixed to mono and reduced to about 22 kHz. The tool measures how much the spectrum changes from moment to moment (spectral flux), which peaks on drum hits and note starts, and then looks for the repeat period of those peaks. A fitted beat grid places each beat on the waveform so you can check it by eye and by ear.

The result is an estimate for music with a steady tempo. The search covers 50 to 200 BPM, with a mild preference for tempos near 120, and half and double time are offered as alternatives when they fall between 30 and 300 BPM.

Confidence and half or double time

Confidence says how regular the pulse is, not whether the number is right. It is high for loops and dance music, and low for speech, ambient music, rubato playing and tracks that speed up or slow down.

The most common mistake of any detector is landing on half or double the tempo you would tap. Use "Count it as" to switch and watch the grid on the waveform: the right choice puts a line on every beat you feel. The click option plays a tick on each grid line over the music.

Limits

One tempo is reported for the whole file, so tracks with tempo changes are averaged, and the grid drifts where the music does. Click playback decodes the first ten minutes of a file; the estimate itself reads the whole file in a stream, so long mixes and podcasts work.

Questions