BPM detector: find the tempo of a song from a file

What this BPM finder does

BPMDetect measures the tempo of recorded music: how many beats per minute the song moves at. It analyses the whole file rather than a short preview, reports the tempo to a tenth of a BPM, and shows its work — the beat grid on the waveform, the alternative readings and a chart of how steady the tempo is from start to finish.

Unlike most online BPM finders, nothing is uploaded. Decoding uses your browser’s Web Audio API and the analysis runs in a background thread on your device, so a folder of unreleased tracks or a two-hour DJ mix is as private as it is on your hard drive. It also means no file-size queue and no daily limit.

How to find the BPM of a song

1. Open your audio. Click Open files or drop one or more MP3, WAV, M4A, OGG, FLAC or video files onto the page. They are decoded in your browser and never uploaded.
2. Read the tempo. The BPM appears with a confidence score and the top candidates. Use ½× or 2× if the result is half or double what you hear, or set a tempo range.
3. Check the beat grid. Click anywhere on the waveform to play from there with a click on every beat. Nudge the grid by 10 ms if it is slightly early or late.
4. Export. For several files, download the results table as CSV or TXT, or copy it to the clipboard.

Why you sometimes get two answers

A song at 128 BPM also repeats every two beats (64) and has eighth notes at 256. Every tempo detector has to pick one of these “octaves”, and the right choice depends on the genre and your use. BPMDetect chooses the most likely one, lists the others with their relation, and lets you switch with one click or fold every result into a range such as 80–160 BPM. Read half-time and double-time BPM for the details.

More than a number

• Beat grid and audition. Click the waveform to play from that point with a metronome click on the detected beats; downbeats are accented.
• Tempo over time. A chart of the local tempo every two seconds shows whether the track is quantised or drifts like a live band.
• Batch and export. Drop dozens of files and download a CSV with BPM, half/double time, confidence and key for each.
• Listen live. Measure music playing in the room with your microphone, or tap along when there are no drums.
• Key estimate. A chroma-based key guess with its Camelot code for harmonic mixing — clearly labelled as an estimate.

Tools

• BPM and key finderSame Camelot number, or ±1, mixes harmonically
• BPM counter (microphone)Move close to the speaker and turn it up
• Batch BPM analyzerSet a tempo range so every track is reported the same way
• BPM from a video fileBeat length in frames = beat ms ÷ (1000 ÷ fps)
• BPM to ms calculatorDelay, reverb and note lengths for any tempo
• DJ pitch calculatorPitch-fader % and semitones between two BPMs
• BPM for runningMatch song tempo to your pace and cadence

Typical BPM by genre

House 118–130Deep house 110–125Tech house 122–130Techno 125–150Trance 130–145Drum & bass 160–180Jungle 155–175Dubstep 136–145Hip-hop 80–115Trap 130–170Reggaeton 88–100Pop 100–130Afrobeats 95–115Amapiano 108–118Dancehall 90–110Lo-fi hip-hop 70–90Disco 110–130Hardstyle 145–160UK garage 128–140

Guides

• How BPM detection worksA plain-English walk through automatic tempo detection: onset strength, spectral flux, autocorrelation, octave errors, comb filters and why live music is harder.
• Half-time and double-time BPM explainedWhy the same song can be 70, 140 or 280 BPM, how producers and DJs decide which number to use, and how to settle octave errors with tapping and context.
• BPM for DJ mixing: matching tempo, pitch and keyHow DJs use BPM: pitch-fader percentages, how far you can stretch a track, key lock, harmonic mixing with Camelot codes, and planning tempo across a set.
• Delay and reverb times from BPMCalculate tempo-synced delay and reverb times: the 60,000 ÷ BPM formula, dotted and triplet notes, pre-delay and decay, LFO rates and sample-accurate loop lengths.
• Finding the tempo of live recordingsLive bands, rehearsals and old records drift in tempo. How to measure the average BPM, see where it speeds up or slows down, and make it usable in a DAW or DJ set.
• BPM vs time signatureBPM measures speed; a time signature describes how beats are grouped. How they interact in 4/4, 3/4, 6/8 and odd meters, and how to convert BPM between beat units.

Frequently asked questions

How accurate is the BPM detector?

On music with a steady beat (most electronic, pop, hip-hop and rock produced to a click) the result is usually within 0.1 BPM of the true tempo. Our automated tests check click tracks and drum patterns at 90, 120, 128 and 174 BPM, with noise and swing, to ±1 BPM. Live recordings that speed up and slow down get an average, and the tempo-over-time chart shows how much they drift.

Are my files uploaded?

No. Files are decoded with your browser’s Web Audio API and analysed by JavaScript on your device. Nothing is sent to a server, so large files and unreleased tracks are fine.

Why does it say 64 when my song is 128 BPM?

Tempo has octaves: a beat at 128 BPM also repeats every two beats (64) and has a pulse on every eighth note (256). The detector picks the most likely level, but it can land on the half or double. Click 2× or ½×, pick another candidate, or choose a tempo range such as 80–160 so the result is always folded into it.

Which formats can I analyse?

Anything your browser can decode: MP3, WAV, M4A/AAC, OGG, Opus and FLAC in all modern browsers, AIFF in Safari, and the audio track of MP4, MOV and WebM videos. You can drop several files at once.

Can it detect the key too?

Yes, as an estimate. A chroma profile of the track is compared with major and minor key profiles and the best match is shown with its Camelot code. Key detection is harder than tempo, so treat it as a starting point and check it by ear — relative keys (C major vs A minor) are the most common confusion.

Does it work on a phone?

Yes. Open a file from your phone’s storage or use Listen with the microphone to measure music playing nearby. On iPhone, files in the Files app can be opened directly.