Contador de BPM e Metrônomo

What BPM is and why it matters

BPM stands for beats per minute — the tempo of a piece of music. A beat is the steady pulse you instinctively tap your foot to, and BPM counts how many of those pulses occur in sixty seconds. Tempo is the single most important number for DJs matching tracks, musicians setting a metronome, dancers choreographing routines, and runners building a playlist that matches their stride. This tool does two jobs in one: a tap counter that measures the tempo of any music you can hear, and a metronome that plays a precise click at a tempo you choose.

How the tap counter calculates tempo

Tapping looks simple but the math is what makes it accurate. Every time you tap, the tool records a high-precision timestamp using the browser's performance.now() clock. It then looks at the gaps between your last several taps — up to the most recent eight — averages them, and converts that average interval to BPM with the formula 60000 / averageGapInMilliseconds. Averaging the recent window smooths out the natural unevenness of human tapping, so a few imperfect taps don't throw the reading off. A result appears after just two taps and tightens as you keep going.

One smart detail: if you pause for more than three seconds between taps, the tool assumes you've started a new song and clears the history, so a stale gap never corrupts the next measurement. You can tap the big circular button or simply press the Space bar, which keeps your eyes on the music instead of the screen.

A worked example

Play a track and tap along on the downbeat. Suppose your taps land 500 milliseconds apart on average. The tool computes 60000 / 500 = 120 BPM and labels it Moderato. Tighten your taps to 400 ms apart and the reading jumps to 60000 / 400 = 150 BPM, now labeled Allegro. The classical tempo names come from a built-in reference scale: Largo (under 60), Adagio (60–76), Andante (76–108), Moderato (108–120), Allegro (120–156), Vivace (156–176), and Presto (above 176). Watching which band lights up tells you not just the number but the musical character of the tempo.

Using the metronome

Switch to the Metronome tab to flip the tool around: instead of measuring tempo, you set one. Choose a BPM from 40 to 220 with the slider or number box, pick a time signature (2/4, 3/4, 4/4, or 6/8), and press Start. The metronome generates its clicks with the Web Audio API rather than playing an audio file, which is why the timing stays rock-solid. It schedules each click slightly ahead of when you'll hear it using the audio clock, so the rhythm doesn't drift even if the browser is busy. The first beat of every bar is accented with a higher-pitched, louder click (1200 Hz versus 880 Hz) so you can feel where the bar begins, and a pulsing circle flashes in time with the audio.

Practical use cases

• DJing and beatmatching. Tap two tracks to find their BPMs, then adjust pitch so they line up for a smooth transition.
• Practicing an instrument. Set the metronome a little slower than performance tempo, nail the passage cleanly, then nudge it up a few BPM at a time.
• Running and cycling cadence. Many runners aim for around 180 steps per minute; tap to a song to check whether it matches your target stride.
• Transcribing or remixing. Quickly identify an unknown track's tempo before importing it into a DAW.

Tips for an accurate reading

• Tap the main pulse, not every note. Aim for the beat you'd clap to, usually the quarter note. Tapping eighth notes will read as double the real tempo.
• Give it several taps. Two taps produce a number, but eight produce a stable one. Let the average settle before trusting it.
• Watch for half- and double-time. If a result looks oddly fast or slow, you may be tapping at twice or half the intended tempo. Songs around 70 BPM are often felt at 140, and vice versa.
• Allow the metronome to use audio. Browsers require a user action before playing sound, so the first Start press both begins the click and unlocks audio — a brief, normal delay.

A note on privacy

Everything happens locally in your browser. The tap timing, the clicks, and the tempo math all run on your device using the Web Audio API and the browser clock — no microphone access is requested and nothing is sent to a server.