Free BPM & Key Finder
Drop an audio file to instantly detect its tempo (BPM) and musical key — right in your browser. No upload, no sign-up.
Drop an audio file here
or click to choose — WAV, MP3, FLAC, M4A, OGG
🔒 Your file never leaves your browser. Analysis runs locally with the Web Audio API — nothing is uploaded.
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Tempo and key are the first thing a brief asks for. TuneLens checks the whole track against a real supervisor brief and tells you whether to pitch it — with the reasoning alongside.
Check a track against a brief →How the detection works
Tempo (BPM)
We build an onset-strength envelope from the audio's spectral flux, then run autocorrelation to find the most consistent beat spacing. The result is folded into the common 70–180 BPM range.
Key
We compute a chromagram — how much energy sits in each of the 12 pitch classes — and correlate it against the Krumhansl-Schmuckler major and minor key profiles to find the best fit.
100% private
Everything runs in your browser with the Web Audio API. Your file is decoded and analyzed locally and never touches a server, so even large lossless files stay on your machine.
Typical BPM by genre
Tempo ranges overlap and there are always exceptions, but most genres cluster around a familiar range. Use this as a sanity check against the detected BPM — and remember that half-time and double-time readings (e.g. 75 vs 150) describe the same groove.
| Genre | Typical BPM |
|---|---|
| Hip-hop / Trap | 80–115 (often felt half-time at 130–150) |
| House / Tech house | 120–128 |
| Techno | 125–135 |
| Trance | 130–140 |
| Dubstep | 140 (half-time feel of 70) |
| Drum & bass | 165–175 |
| Pop | 100–130 |
| Ballad / R&B | 60–90 |
Why BPM and key matter
Knowing a track's tempo and key is the foundation of almost everything you do with it. DJs beatmatch and harmonically mix by BPM and key. Producers pitch samples, line up loops, and pick complementary stems. Songwriters find the right key for a vocal range, and sync musicians match the energy a brief asks for. Getting these two numbers right up front saves hours of guesswork later.
Key detection is a best estimate, not an absolute — a key and its relative major or minor share the exact same notes, so we show the relative key and a confidence level alongside the result. Trust your ear as the final word, especially on modal or ambiguous material.
Frequently asked questions
How do I find the BPM of a song?
Drop an audio file onto this page and it detects the tempo automatically. The tool analyzes the rhythmic onsets in the audio and measures the time between beats to calculate beats per minute. It works on MP3, WAV, FLAC, M4A and OGG files, entirely in your browser.
How accurate is automatic key detection?
Key detection analyzes the distribution of pitch classes and matches it to major and minor key profiles. It's accurate for most tonal music, but ambiguous or modal material is harder. Because a key and its relative major/minor share the same notes, we also show the relative key and a confidence level so you can sanity-check against your ear.
Why does the BPM sometimes show double or half?
Tempo is ambiguous by octaves — 70 BPM and 140 BPM describe the same groove counted differently. This tool folds results into the common 70–180 BPM range, but if a result feels off by a factor of two, trust the feel of the track. Both readings are musically valid.
Is the BPM and key finder free and private?
Yes. It's completely free with no sign-up, and runs entirely in your browser using the Web Audio API. Your audio file is decoded and analyzed locally and never leaves your device.