BPM Detector

What the BPM Detector Does

The BPM Detector finds the tempo of an audio file and reports it in beats per minute. MP3, WAV, OGG, AAC, FLAC, and other browser-playable files are decoded locally, analyzed for repeating beat patterns, and scored with a confidence percentage. Nothing is uploaded: the file is read, decoded, and analyzed entirely on your device.

Along with the main reading, the tool lists possible tempos at half and double time and shows the file's duration, sample rate, and channel layout so you can confirm you analyzed the right track.

How to Detect the BPM of a Song

Drop an audio file onto the upload area, or click it to browse your device.
Wait while the file is decoded and the analyzer measures repeating beat intervals.
Read the detected BPM and the confidence score next to it.
Compare the possible tempos list if the reading sounds like half or double the pulse you hear.
Load the built-in 128 BPM sample click track at any time to see how a clean detection looks.

How Automatic Tempo Detection Works

The decoded audio is scanned for onsets, the short energy spikes created by drums, plucks, and other percussive sounds. The tool then measures how strongly those onsets repeat at each candidate beat interval between roughly 40 and 220 BPM. The interval with the strongest periodic repetition wins and is converted into beats per minute.

To keep results fast, only the first 60 seconds of a longer file are analyzed. Tempo is normally constant across a track, so this window is enough for a reliable reading while avoiding minutes of processing on full-length songs.

Reading the Confidence Score

Confidence reports how clearly the detected interval dominates the rhythm of the track. A high score means the beat pattern repeats strongly and the reading is reliable. A low score usually means the audio is ambient, rubato, or produced with heavy reverb and swing, so no single interval stands out. In those cases, use the BPM Tap Tempo tool and tap along with the beat instead.

Half Time and Double Time

Many songs can be counted at two speeds. A marching track at 128 BPM can also be heard as 64 BPM if you count every other beat, and a slow ballad at 70 BPM can feel like 140 BPM when counted in double time. Musicians and DJs choose the count that matches how the song feels, so the tool lists both options next to the detected value. Compare them against the natural pulse of the track and pick the one that fits your project.

Tips for Better Results

Use an audio file rather than a video recording whenever possible; compressed speech and camera noise hide the beat.
Excerpts with a clear drum loop or steady rhythm detect best.
If the score is low, check the half and double time options before trying another file.
For DJ sets or classical pieces, tap the tempo manually for a reading that matches your ears.

Related Music Tools

BPM Calculator converts a tempo into beat and note durations, or finds BPM from a measured bar length.
Tone Generator produces steady reference tones and click-like signals for practice.
Audio Speed Changer slows a track down without changing its pitch, which is useful for transcribing fast parts.
Audio Equalizer boosts the low end so kick drums stand out before you re-run detection.

Frequently Asked Questions

How accurate is automatic BPM detection?

For produced music with a steady beat, the detected tempo is usually exact or within a fraction of a BPM. Live recordings, swing rhythms, and ambient tracks are harder, so the tool reports a confidence score and suggests half and double time readings. When the score is low, tapping the tempo manually is the most reliable option.

Why does it only analyze the first 60 seconds?

Tempo is normally constant across a song, so a one minute window contains hundreds of beats, which is more than enough to find the interval. Limiting the window keeps analysis fast even for long files, and the result card notes when a file was only partially analyzed.

Is my audio uploaded to a server?

No. The file is decoded and analyzed in your browser with the Web Audio API. It never leaves your device, nothing is stored, and no network request carries the audio. The page keeps working offline once loaded.

Which file formats are supported?

Any audio format your browser can decode: MP3, WAV, OGG, AAC, FLAC, M4A, WebM audio, and others. Support depends on the browser, but every major browser handles MP3 and WAV, which covers most use cases.

Can I detect the tempo of a video file?

The file picker accepts audio formats. If you only have a video, extract the audio track first with the Audio Splitter, then run the extracted audio through the detector.

What does it mean when the confidence is low?

Low confidence means the audio does not repeat strongly at any single beat interval. The tool still reports its best guess, but you should verify it by ear or tap the tempo manually. Speech recordings, pads, and free-time music often score low.

Report