What is the arithmetic?

Sixty thousand milliseconds in a minute, divided by the tempo, gives one beat. At 120 beats per minute that is 500 milliseconds for a quarter note. Every other length is a fraction of it: an eighth is half, a sixteenth is a quarter, and so on down.

What does the dotted figure mean?

A dot adds half the note's length again, so a dotted eighth is three quarters of a beat. A triplet fits three notes in the space of two, so a quarter triplet is two thirds of a beat. Both are listed because both are what a rhythmic delay is usually set to.

Why is a rate in hertz shown as well?

Because an LFO takes a rate rather than a time, and the two are reciprocal. A delay of 250 milliseconds is 4 Hz, so setting a tremolo to 4 Hz at 120 beats per minute puts it on the eighth note. Reading it off the number rather than the knob position is what makes the part lock in.

BPM to Delay Time

A tempo in, every note length in milliseconds out.

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Tempo

A tempo in, every note length in milliseconds out.

How to use it

Type the tempo. Beats per minute, anywhere from 20 to 400.
Find the note length. Whole down to thirty second, each one with its dotted and triplet form.
Take the milliseconds or the hertz. Milliseconds for a delay, hertz for an LFO or a tremolo rate.

When you would use this

A delay set by ear drifts. A delay set from the tempo lands on the beat, and the arithmetic behind it is one division: sixty thousand milliseconds in a minute, divided by the tempo, gives the length of a quarter note. Everything else is a fraction of that. An eighth is half, a sixteenth is a quarter, a dot adds half again, and a triplet fits three in the space of two, which is two thirds. At 120 beats per minute a quarter note is 500 milliseconds and a dotted eighth is 375, and those two together are the sound most people mean by a rhythmic delay. Each row also carries the rate in hertz, because that is the unit an LFO takes. A tremolo at the eighth note rate at 120 beats per minute is 4 Hz, and setting it by the number rather than by the knob position is the difference between a part that locks in and one that nearly does. The range covers 20 to 400 beats per minute.

Questions

What is the arithmetic?: Sixty thousand milliseconds in a minute, divided by the tempo, gives one beat. At 120 beats per minute that is 500 milliseconds for a quarter note. Every other length is a fraction of it: an eighth is half, a sixteenth is a quarter, and so on down.
What does the dotted figure mean?: A dot adds half the note's length again, so a dotted eighth is three quarters of a beat. A triplet fits three notes in the space of two, so a quarter triplet is two thirds of a beat. Both are listed because both are what a rhythmic delay is usually set to.
Why is a rate in hertz shown as well?: Because an LFO takes a rate rather than a time, and the two are reciprocal. A delay of 250 milliseconds is 4 Hz, so setting a tremolo to 4 Hz at 120 beats per minute puts it on the eighth note. Reading it off the number rather than the knob position is what makes the part lock in.