BPM Tapper

How to use the BPM tapper

1. Play the song and listen for a bar or two to find the beat, usually the kick drum or the snare.
2. Tap the pad on each beat. On a computer you can also press T anywhere on the page, or Space or Enter when the pad has focus. On a phone, tap the pad with a finger.
3. Keep tapping for about two bars. The tempo appears from the second tap and steadies as the taps add up; the bar under the readings shows how many intervals are in the average.
4. Stop when the number settles. The reading stays on screen. Copy the rounded tempo, or click any value to copy it, and set your DAW to it. Press Reset to start again, or simply pause for two seconds and tap a new count.

The ring around the pad and the small lamp above the reading blink at the measured tempo, starting from your last tap. If they stay with the kick while the song plays, the reading is right.

How tap tempo is calculated

Each tap is timed with the browser's high-resolution clock. The tapper takes the average gap between your taps in milliseconds and converts it to beats per minute:

BPM = 60,000 ÷ average interval in ms

Why more taps help. Nobody taps with perfect timing, and with only two taps the whole reading rests on one interval. At 120 BPM a beat lasts 500 ms, so tapping one beat 20 ms late turns a two-tap reading into about 115 BPM. The tapper averages up to the last eight intervals (nine taps), and the average depends on the time from the first of those taps to the last, so the same 20 ms slip moves a nine-tap reading by about 0.6 BPM. Four taps already bring it under 2 BPM. Older taps drop out of the window as you keep going, so the reading follows a song that speeds up or slows down.

Why a pause starts a new count. When more than two seconds pass between taps, the next tap starts a fresh count instead of being averaged with taps from a different moment, or a different song. The last reading stays on screen until the new count has two taps. The same two second limit means the slowest tempo you can tap is 30 BPM; readings above 300 BPM show as 300.

Why a stray tap does not ruin it. If one interval is more than 40 percent shorter or longer than the average so far, which is what a missed beat or an accidental double tap looks like, the count restarts from the last two taps. The reading jumps briefly and recovers within a tap or two of steady tapping, instead of carrying the error through the next eight. The result is shown to one decimal place, with a whole-number version beside it.

Half time or double time?

A groove has a pulse at several levels at once: the hi-hats, the kick, and the snare or clap backbeat. Tap any of them steadily and the tapper reports that pulse correctly, which is why the half-time (÷ 2) and double-time (× 2) readings sit next to the result. Usually only one of the three matches the tempo the song was made at.

• Check the snare. In most pop, rock, hip-hop and house the snare or clap lands on beats 2 and 4. If you tapped only the snare, you tapped every other beat: use the double-time reading.
• Check the genre. House usually sits around 120 to 130 BPM. Trap is usually counted at 130 to 150 BPM even though it feels half as fast, and drum and bass is counted at around 170 to 176 BPM even when the drums feel like 85. If your reading is near half of the usual range, try the double.
• Check the bars. Set the DAW to the reading and play the song against the grid. Sections usually run 4, 8 or 16 bars. If an eight-bar verse fills only four bars of the grid, the tempo is half what it should be; if it fills sixteen, it is double.

Tips for an accurate reading

• Tap the kick or the snare. They are the clearest, most regular hits. Hi-hats are fast enough to tire your hand, and vocals and bass lines are often syncopated.
• Tap for two bars. Nine taps fill the averaging window. If the number is still moving after that, your timing is drifting; take a breath, pause for two seconds and start a new count.
• Use the input you are steadiest with. A key, a mouse button and a finger on a phone screen are all timed the same way. A constant delay, from Bluetooth headphones or a slow screen, does not change the result, because only the gaps between taps count.
• Try the rounded value first. Songs made in a DAW are usually set to a whole-number tempo, so a reading of 127.6 is most likely 128. Live recordings made without a click drift, so a tap reading is the average for the passage you tapped.
• Nudge it in the DAW. Line the song's first downbeat up with a bar line and listen several bars in. If the beats start to land ahead of the grid, raise the tempo by 0.5 or 1 BPM; if they fall behind, lower it.

Finding BPM from an audio file

Tapping works for anything you can hear: a stream, a record, a phone video or a band in the room. When you have the audio file itself, the Key and BPM Finder measures the tempo from the file and also gives you the key, its Camelot code and the tuning. It runs in your browser too, and the audio never leaves your computer.

The two tools suit different jobs. The finder reads tempos between 70 and 180 BPM and shows the half-time and double-time values beside them, and a beatless pad or ambient piece can read as having no steady beat. The tapper takes whatever pulse you feel, from 30 to 300 BPM, including songs that speed up and slow down. Once you have the tempo, the delay calculator turns it into delay times in milliseconds and hertz.