BPM to delay and reverb time calculator

How to use it

Type the song's tempo. If you do not know it, find it with the tap tempo counter, which links straight back here with the tempo filled in. The first table lists every note value from a whole note down to a sixty-fourth, each in three feels. Pick the one you want and type the milliseconds into your delay, or use the Hz column for anything with a rate control.

The note names assume the beat is a quarter note, as in 4/4, 3/4 and most DAW tempo settings. In 6/8 with a dotted-quarter tempo, convert first: a dotted-quarter tempo of 80 is an eighth-note tempo of 240 and a quarter-note tempo of 120.

The formula

• quarter note (ms) = 60,000 / BPM
• note (ms) = quarter note × length in quarters (whole = 4, half = 2, eighth = 0.5, sixteenth = 0.25)
• dotted = note × 1.5, because a dot adds half the note's value
• triplet = note × 2/3, because three triplets fill the time of two
• rate (Hz) = 1000 / note (ms)

Worked example. At 128 BPM, a common house tempo, a quarter note is 60,000 / 128 = 468.75 ms. An eighth is half that, 234.38 ms. A dotted eighth is 234.38 × 1.5 = 351.56 ms, and an eighth-note triplet is 234.38 × 2/3 = 156.25 ms. A tremolo synced to sixteenths runs at 1000 / 117.19 = 8.53 Hz.

Tempo-synced reverb

The reverb table follows a widely taught convention: choose a musical length for the whole reverb, set pre-delay to a very short note value (a 1/64 note by default) so the dry sound stays clear before the reflections arrive, and set the decay to the remainder, so pre-delay plus decay equals the chosen length. At 120 BPM, a quarter-note reverb is 31.25 ms of pre-delay and 468.75 ms of decay.

Be aware that "decay" means different things in different reverbs. Many use RT60, the time for the tail to fall by 60 dB, which is audible for noticeably less time than that in a busy mix. Others use their own scale. Treat the numbers as a starting point and trust your ears.

Where it stops being reliable

The arithmetic is exact; the limits are practical. Some hardware delays only accept whole milliseconds, so a value like 351.56 ms rounds to 352 ms and the repeats drift by half a millisecond per echo, which is inaudible for a handful of repeats but can build up with long feedback. Songs recorded without a click are not at one fixed tempo, so a synced delay can move against the performance. And analogue and tape-style delays often have a time knob with no accurate scale at all, so set them by ear against the tempo from a metronome.