BPM Calculator
This BPM calculator converts a tempo in beats per minute into the length of each beat in milliseconds, along with the durations of the common note values musicians and producers actually use: the eighth note, the sixteenth note and a full bar of 4/4. Type a tempo and the timings update instantly, or use the tap tempo button to find the BPM of a song you are listening to: tap in time with the beat and the calculator averages the gaps between your taps to estimate the tempo, filling the BPM box for you. Producers use these numbers constantly. Delay and reverb effects sound tightest when their times are locked to the tempo, so a quarter note delay at 120 BPM should be 500 ms, an eighth note 250 ms, and a reverb pre-delay is often set near a sixteenth note. DJs use BPM to plan transitions between tracks, drummers use it to programme click tracks, and video editors use bar lengths to cut footage on the beat. The calculator assumes a 4/4 time signature for the bar length, which covers the vast majority of popular music, and every figure is a straight division of the 60,000 milliseconds in a minute.
Tap along with the beat for at least four taps. The count resets if you pause for more than 2.5 seconds.
Note durations assume a 4/4 time signature with the beat on the quarter note. For dotted notes, multiply the plain note value by 1.5; for triplets, multiply by two thirds.
How it works
BPM stands for beats per minute, and a minute is 60,000 milliseconds, so the length of one beat is simply 60,000 divided by the tempo. Everything else follows from that one number: an eighth note is half a beat, a sixteenth note is a quarter of a beat, and a bar of 4/4 is four beats. The tap tempo button works in reverse. Each tap is timestamped, the calculator averages the gaps between your taps, and 60,000 divided by that average gap is the tempo. The more taps you give it, the steadier the estimate, because one slightly early or late tap matters less across a longer run. Pause for more than 2.5 seconds and the taps reset so a stray click does not pollute the next measurement.
Worked example
Take a track at 120 BPM, the default here and a very common tempo for pop and house. One beat is 60,000 / 120 = 500 ms, so a quarter note delay should be set to 500 ms. An eighth note is 250 ms, which is the classic setting for a slap-back or rhythmic delay, and a sixteenth note is 125 ms, useful for tight pre-delay on a reverb. A full bar of 4/4 lasts 4 x 500 = 2,000 ms, so a one-bar loop is exactly two seconds long. If you wanted a dotted eighth delay, the trick behind many famous guitar and synth lines, you would multiply 250 ms by 1.5 to get 375 ms.
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