Syncing delay and reverb to your tempo: the BPM-to-milliseconds guide

There's a reason a delay can sit invisibly inside a mix on one setting and turn into a muddy mess two milliseconds later. Time-based effects — delay, echo, reverb pre-delay — either lock to the groove of the song or fight it. When the repeats land on the beat, the ear hears them as part of the rhythm. When they land between beats, the ear hears clutter. The difference is arithmetic, and it's worth understanding rather than dialing by ear every time.

The one formula you need

A quarter note's length in milliseconds is:

ms = 60000 / BPM

Sixty thousand because there are 60,000 milliseconds in a minute, and BPM counts quarter notes per minute. At 120 BPM a quarter note is 60000 / 120 = 500 ms. Everything else is just multiplying or dividing that quarter-note value:

• Whole note: quarter × 4
• Half note: quarter × 2
• Eighth note: quarter ÷ 2
• Sixteenth note: quarter ÷ 4

So at 120 BPM you get 2000 / 1000 / 500 / 250 / 125 ms for whole through sixteenth. Memorize the quarter note for your tempo and you can derive the rest in your head.

Dotted and triplet times — where the groove lives

Straight divisions are only half the story. The two values that make delays feel musical are dotted and triplet times.

A dotted note is 1.5× its straight value. A dotted eighth at 120 BPM is 250 × 1.5 = 375 ms. This is the single most famous delay setting in popular music — the dotted-eighth delay is the shimmering, syncopated repeat behind countless guitar and synth lines. It works because the repeats fall just off the straight eighths, weaving a counter-rhythm against the beat instead of doubling it.

A triplet note is 2/3 of its straight value. A triplet eighth at 120 BPM is 250 × 0.667 ≈ 167 ms. Triplet delays give a rolling, galloping feel — great for fills and half-time sections.

The practical move: set a delay to a dotted-eighth and a second delay to a straight quarter, pan them apart, and you get width and rhythmic interest without washing out the source.

Reverb is a tempo effect too

Most producers sync delays and then set reverb by ear. But reverb has two time parameters that benefit from the same math.

Pre-delay — the gap before the reverb tail starts — is really just a very short delay. Setting it to a sixteenth or a thirty-second note (say 60–125 ms at 120 BPM) keeps the dry transient clear and pushes the wash of the tail onto a beat subdivision, so the reverb breathes with the track instead of smearing across it.

Decay time can be tuned so the tail fades out roughly as the next hit lands — often around one beat or a dotted-quarter for a vocal, longer for a sparse ballad. A reverb that decays in time with the song clears space for the next phrase; one that ignores the tempo piles up into mud on busy material.

What about hertz?

The same quarter-note value flips into a frequency for tempo-synced modulation. Frequency in hertz is just 1000 / ms. A quarter note of 500 ms is 2 Hz — set a tremolo or filter LFO to 2 Hz at 120 BPM and the wobble locks to the beat. This is how you get auto-pan, sidechain-style pumping, and filter sweeps that move with the song rather than drifting against it.

When not to sync

Locking to tempo is a default, not a law. Two cases where free timing wins:

• Slapback echo on vocals or rockabilly guitar — a single short repeat around 80–120 ms, deliberately not on a subdivision, for thickness without an audible rhythm.
• Lush ambient washes where you want the reverb and delays to blur into an undefined cloud. Syncing would make the repeats too rhythmically legible.

And remember the formula assumes BPM counts quarter notes. In a compound meter like 6/8 where the dotted quarter is the felt beat, you may want to base your divisions on that instead — the math is the same, you're just choosing a different reference note.

Skip the mental arithmetic

Doing 60000 / BPM and then chasing every dotted and triplet variant by hand gets old fast, especially at odd tempos like 137 BPM. Our BPM to delay & reverb time calculator takes a tempo and time signature and prints the full chart — whole through 1/32 notes, with dotted and triplet columns, in both milliseconds and hertz — plus tap-tempo if you only know the groove by feel. Set your delays and pre-delay straight from the table, and your time-based effects start working with the track instead of cluttering it.