Pre-Delay Calculator
Pre-delay is the short silence before the reverb tail begins. Set it to a small note value at your tempo and the source stays clear, close and intelligible — even inside a long tail.
| Note | Pre-Delay |
|---|---|
| 1/32 | 62.5 ms |
| 1/64 | 31.25 ms |
| 1/128 | 15.63 ms |
| 1/256 | 7.81 ms |
| 1/512 | 3.91 ms |
Rule of thumb: longer pre-delay for vocals (clarity), shorter for drums (glue).
The method: borrow a very small note value
A reverb unit starts its tail the instant it receives signal unless you tell it to wait. That waiting time is the pre-delay, and the useful range is tiny — usually somewhere between about 4 ms and 125 ms depending on tempo and source. Random numbers in that range work, but note values work better, because a gap that is itself a musical subdivision starts the tail at a moment the rhythm already makes sense of.
pre-delay (ms) = quarter note × small note fraction
decay = total − pre-delay
The candidates are the fast end of the note table: a 1/32 note is 1/8 of a quarter, a 1/64 is 1/16, a 1/128 is 1/32, a 1/256 is 1/64 and a 1/512 is 1/128. Picking one is not just tidiness — because this site holds decay equal to total minus pre-delay everywhere, a longer pre-delay automatically shortens the decay by the same amount, so the end of the tail stays exactly where you planned it. Change the gap and the tail still resolves on the grid.
Pre-delay is one half of the combined console on the home page reverb calculator, where the four standard sizes each ship with a suggested gap already subtracted. This page isolates the gap so you can size it for a specific source.
Reference table: pre-delay note values at 90, 120 and 150 BPM
Three representative tempos show how quickly the useful gap shrinks as songs speed up. The same 1/64 note that feels spacious at 90 BPM is a tight 25 ms at 150 BPM — one more reason to calculate from tempo instead of memorizing a single favorite number.
| Note value | At 90 BPM (ms) | At 120 BPM (ms) | At 150 BPM (ms) |
|---|---|---|---|
| 1/32 | 83.33 | 62.5 | 50 |
| 1/64 | 41.67 | 31.25 | 25 |
| 1/128 | 20.83 | 15.63 | 12.5 |
| 1/256 | 10.42 | 7.81 | 6.25 |
| 1/512 | 5.21 | 3.91 | 3.13 |
Values under roughly 10 ms add size without an audible gap; values from about 20 to 65 ms are the clarity workhorses; and anything approaching a 1/32 at a slow tempo starts to separate into a distinct slap, which is an effect in its own right rather than a transparent gap.
Sizing the gap by source
Why a gap preserves clarity and transients
Your ear locates and identifies a sound from its first few milliseconds — the pick attack, the consonant, the stick hit. If the wash starts at the exact same instant, those defining transients are competing with thousands of reflections and the source feels further away and less articulate, even at the same volume. A short pre-delay lets the dry attack speak first and the reflections arrive just afterward, so the brain files the sound as close and clear with a space behind it. It is the cheapest intelligibility in mixing: no EQ, no volume change, just a few milliseconds of patience.
Vocals: lean longer
Words are transient information, so lead vocals usually take the longest gaps on this page — a 1/32 or 1/64 note is a good audition range, 62.5 or 31.25 ms at 120 BPM. Ballads with long tails benefit most, because the gap is doing the work of keeping lyrics upfront while the decay provides the drama behind them. The genre-by-genre pairings of gap and tail live on the vocal reverb settings by genre page, which builds its presets around exactly this trade-off.
Drums and percussion: lean shorter
Drum hits are almost pure transient, but they are also frequent — a long gap before every snare wash can start to feel disconnected from the kit. A 1/64 or 1/128 note (31.25 or 15.63 ms at 120 BPM) usually separates the crack of the hit from the bloom without detaching them. For tails that must end before the next backbeat, pair a short gap with the snare timing rule and full drum targets, where the gap and the total are worked out together.
Guitars, keys and pads: shortest of all
Sustained sources have little transient to protect, so their gaps can shrink toward a 1/256 or 1/512 note — 7.81 or 3.91 ms at 120 BPM — where the pre-delay is mostly preventing a smeared attack rather than creating audible separation. Pads often want no deliberate gap at all beyond the smallest value, since their whole purpose is to be a continuous bed.
Limitations
Pre-delay cannot rescue a tail that is simply too long or too loud; it protects the beginning of a sound, not the space after it — that is the job of the decay setting covered by the decay calculator that keeps tails on the grid. Very long gaps at slow tempos can also detach the reverb from the source entirely, turning one performance into a call and response. And in dense arrangements the ideal gap differs per source, which is why busy mixes often run two or three reverb sends with different pre-delays rather than one shared setting. Treat the table as a musically sensible starting grid, then adjust in a few-millisecond steps while listening to the dry attack.
Frequently asked questions
What exactly is reverb pre-delay?
It is the delay between the dry sound reaching the reverb and the first reflections coming back — a short, deliberate pause before the tail starts. On most plugins it is a single control in milliseconds, typically somewhere between 0 and 125 ms for music work. This page ties that pause to a note value at your tempo.
How many milliseconds of pre-delay should a vocal have?
Start with a 1/64 or 1/32 note at your tempo: 31.25 or 62.5 ms at 120 BPM, and 25 or 50 ms at 150 BPM. Slower, more exposed vocals tolerate and benefit from the longer end; fast, dense lyrics usually sit better nearer the shorter value. Always check that words stay understandable at low playback volume.
Does pre-delay change the total reverb time?
On this site, no: decay is always calculated as total minus pre-delay, so lengthening the gap shortens the decay by the same amount and the tail still ends on the same beat. Some plugins behave differently and add the gap on top of the set decay, so check whether your unit labels its main control as decay time or total time.
Can pre-delay be too long?
Yes. Past roughly a 1/32 note at a slow tempo — 83.33 ms at 90 BPM — the gap becomes audible as a separation, and the reverb starts to sound like a distinct echo answering the source rather than a space around it. That can be a deliberate effect, but as a default it usually breaks the illusion.
Why use a note value instead of a round number like 30 ms?
A round number is fine in isolation, but a note value scales with the song: change tempo and the gap changes proportionally, keeping the same rhythmic relationship. A fixed 30 ms is a 1/64 note at 125 BPM but a full 1/128 note at half that tempo. Note values keep the intention identical across songs.
- Wikipedia — Reverberation — How direct sound and later reflections are perceived as one event or as separate spaces.
- iZotope — Learn — Vocal and mixing guides on using pre-delay to keep sources upfront inside a tail.
- Sound on Sound — Practical reverb technique, including pre-delay choices for vocals and drums.