Why Milliseconds Matter More Than BPM
Your DAW knows the tempo, but your ears hear time. When you dial 380 ms into a delay plugin, you are really asking for a dotted eighth note at 118 BPM — and if the song is actually at 124, that echo lands late, smearing the groove instead of driving it. Tempo-synced delay (1/8D, 1/4T) solves this inside the DAW, but hardware pedals, outboard delays, reverb pre-delay knobs, and LFO rate controls all speak milliseconds and hertz. This calculator is the translator.
The core math is disarmingly simple: one beat lasts 60,000 divided by BPM milliseconds. At 120 BPM a quarter note is exactly 500 ms; at 100 BPM it is 600 ms; at 140 it is about 428.6 ms. Every other note value is a multiple or fraction of that beat — a half note doubles it, an eighth halves it, a sixteenth quarters it. Dotted notes stretch any value by 1.5×; triplets squeeze three notes into the space of two, multiplying by 2/3.
The Note Values You Will Actually Use
In real sessions, five note values cover 95% of delay work. Quarter-note delay is the big spacious echo — think U2-style washes. Dotted eighth is the famous rhythmic delay: the echo lands between your notes, creating that galloping, interlocking pattern. Eighth note is the tight slapback that thickens vocals without obvious echo. Triplet eighth fits swung and shuffle grooves where straight divisions fight the feel. Sixteenth at higher feedback gives mechanical, almost reverb-like textures.
The table above lists all seven standard values — whole through 64th — because sound design sometimes wants the extremes. A whole-note delay at 90 BPM is 2,667 ms of cavern; a 64th at 160 BPM is 23 ms, well into chorus/flange territory where "delay" becomes "tone".
Dotted vs Triplet: Feel the Difference
Dotted and triplet are not just math — they are groove decisions. A dotted eighth (0.75 beats) creates syncopation against straight playing: the echo answers in the gaps. That is why it defines entire genres of guitar music. A triplet eighth (0.333 beats) divides the beat into three equal parts, which locks with shuffles, swung hi-hats, and 6/8 feels where straight eighths would sound rushed.
Quick rule of thumb: if the drums swing, reach for triplets; if they play straight, reach for dotted. Mixing a straight-eighth delay onto a swung track is one of the most common reasons "the delay sounds wrong but I can't say why."
Tap Tempo: Stealing the Tempo From the Room
Sometimes there is no BPM — a live band drifting, a vinyl sample, a drummer who "feels" 96 but plays 99. That is what the TAP pad is for: tap quarter notes along with the music (at least three or four taps) and the calculator averages your intervals into a BPM. Tap on the downbeats, keep your taps even, and ignore the first wobbly one — the average of the last several taps is what counts.
Pro tip: tap for a full 8 bars if you can. Short tap runs exaggerate your own timing wobble; longer runs average it out. And tap the subdivision you will delay — if you want quarter-note echo, tap quarters, not eighths.
Reverb Pre-Delay in Milliseconds
Pre-delay — the gap between the dry sound and the start of the reverb — is where mixes gain clarity. Set it to a 16th or 32nd note of the tempo and the reverb breathes with the track instead of washing over it: vocals stay intelligible, snares stay punchy. At 120 BPM, try 125 ms (16th) for vocals and 62.5 ms (32nd) for drums. Too long and the reverb detaches into an audible echo; too short and it might as well be zero.
A useful trick: set pre-delay to a dotted 16th for a subtle push — it lands just behind the grid, adding movement without obvious repetition. The calculator's dotted column gives you these odd-but-musical values instantly.
Hz for LFOs: The Other Direction
Tremolo, autopan, filter sweeps, and chorus LFOs are often calibrated in hertz, not note values. The conversion: Hz = BPM / 60, then divide by the note value in beats. A quarter-note LFO at 120 BPM is 2 Hz; an eighth-note LFO is 4 Hz; a half-note swell is 1 Hz. The readout above the table shows the quarter-note Hz for your tempo — multiply or divide by two per note value from there.
Watch out for LFOs that only accept whole Hz: at 100 BPM a quarter-note pulse wants 1.667 Hz, which rounds to 2 Hz (120 BPM equivalent) on coarse knobs — close enough for tremolo, noticeably off for rhythmic gating. When precision matters, use the DAW's synced LFO instead.
Delay Without a DAW: Pedals and Hardware
Guitarists with analog delay pedals live in milliseconds: a single Time knob, no sync. Dial the table value for your song's tempo before the gig and mark it — many players keep a tempo card taped to the pedalboard with ms values for the setlist. Digital pedals with tap-tempo footswitches do the math for you, but knowing the ms value lets you sanity-check that the pedal heard you right (a double-time mis-tap is obvious when you know 500 ms was the target).
For slapback on rockabilly guitar or vocals, start at 80–140 ms regardless of tempo — slapback is a fixed psychoacoustic effect, not a rhythmic one. Tempo-synced slap (eighth or 16th) is a different, more modern sound; both are valid, they just do different jobs.
Common Mistakes
The classic error is delaying in the wrong subdivision — quarter-note echo on a busy 16th-note guitar part turns to mush; the busier the part, the shorter the subdivision should be. Second is too much feedback with long times: beyond 3–4 repeats, rhythmic delays become ambient washes, so commit to one identity or the other. Third is ignoring stereo: offsetting left and right delays by a few milliseconds (or a dotted vs straight pair) creates width that mono delays cannot.
And the meta-mistake: calculating to three decimals and then not listening. The table gets you to the mathematically right neighborhood; nudge ±5–10 ms by ear from there. Groove lives in the nudge.
Syncing Hardware: MIDI Clock vs Milliseconds
Modern pedals and synths often accept MIDI clock, which syncs them to the DAW's tempo automatically — no math required. But plenty of beloved gear (analog delays, older rack units, guitar pedals) only speaks milliseconds, and even MIDI-synced devices drift when the clock source is a shaky live drummer. Knowing the ms values makes you the person who can dial in anything: read the table, set the knob, done.
When syncing hardware to a DAW, set the DAW as clock master and the pedal as slave, then verify by ear — MIDI clock jitter of a few milliseconds is normal and usually inaudible on delays, but it can smear tight rhythmic gates. For critical parts, print the effect to audio: once it is a waveform, timing is frozen forever and your mix recalls perfectly next month.
Putting It All Together
The workflow that never fails: get the true tempo (tap it if you must), pick the subdivision that serves the part, read the ms value, dial it in, then nudge by ear. Dotted eighths for rhythm, eighths for slap, 16ths for pre-delay clarity, triplets for swing. Keep this page open in the studio and tempo math becomes a glance instead of a chore — which means you will actually do it, every time, instead of guessing 350 ms and hoping.