Delay Time Calculator

A delay that repeats in time with the music sounds like part of the groove. One that does not sounds like an echo from another song. If your delay pedal or plug-in asks for a time in milliseconds, you need to turn the tempo of the track into a time, and for every note value you might want: eighth notes, dotted eighths for the classic rhythmic echo, triplets. This calculator makes the table in one step.

The arithmetic

A minute has 60,000 milliseconds, so a beat at 120 BPM lasts 60,000 ÷ 120 = 500 ms. A quarter note is one beat, a half note two, a whole note four, an eighth half a beat and a sixteenth a quarter of a beat. Dotted notes are one and a half times as long as the straight value, because the dot adds half; triplets fit three notes where two would go, so each is two thirds as long.

A worked example

At 120 BPM the table gives a quarter note of 500.0 ms, dotted quarter 750.0 ms and quarter-note triplet 333.3 ms. A sixteenth note is 125.0 ms. One beat is 500 ms and a bar of 4/4 is 2,000 ms. Switch Show as to Hertz and a quarter note becomes 2 Hz, the rate for a tremolo or a chorus that completes one cycle per beat. Switch to Seconds for the same times in seconds, 0.5 and 0.75.

The classic settings

A dotted-eighth delay against a straight-eighth guitar part gives the rolling effect of many famous rock guitar sounds. A quarter-note delay repeats on every beat and leaves space between repeats. Triplet delays make a shuffling feel. For a slap-back, a short time in the range of 80 to 120 ms is typical, though no note value of the tempo is needed. Tempo-synced delays are easiest to use when the feedback is set low enough that the repeats die away before the next phrase.

Reverb pre-delay and decay

The second table gives pre-delay values at fractions of a beat, with a short explanation of what each is good for, and a decay time that ends on the next beat. At 120 BPM they are 31.25 ms, 62.5 ms and 125 ms for pre-delay, and 500 ms for a decay that dies just as the next hit arrives. For a longer tail use two or four beats. These are starting points to adjust by ear, not rules.

Edge cases

Tempos with decimals work: 93.5 BPM gives a beat of 641.7 ms. Some plug-ins express delay time in samples; to convert, multiply milliseconds by the sample rate and divide by 1,000. A tempo change inside a song needs a new table at each tempo. Hardware often rounds to whole milliseconds, which is inaudible for single repeats but can drift in long feedback loops.

Limits

The page gives times, not an effect. The table lists a set of common note values, not every possible one, and the pre-delay and decay figures are common guidelines rather than measured values for a room. Everything is calculated locally.

Related tools

• Tap Tempo finds the BPM of a song when you do not know it.
• Note Frequency Chart has a similar note-length table next to the pitch chart.
• Polyrhythm Metronome plays two rhythms against each other.
• Sample Pitch Calculator works out the effect of speeding a sample up or down.