Delay and Reverb Calculator — In Sync

An echo that ignores the tempo is just noise arriving late. Enter your track’s BPM and this calculator returns the delay times that lock to the music — every note value from whole notes to sixteenths, plain, dotted and triplet — plus the pre-delay figures that keep a reverb from swallowing the words it was hired to beautify.

Milliseconds Are Note Values in Disguise, Always

A beat lasts 60,000 ÷ BPM milliseconds, and every delay time a producer has ever loved is that beat multiplied by a note value: the quarter is ×1, the eighth ×½, the dotted eighth ×¾, the triplet quarter ×⅔. Tempo-synced delay works because the repeats land on the grid — the echo becomes a rhythm section rather than a smear — and the calculator is the multiplication table for any tempo, replacing the laminated charts taped to studio walls since the first digital delay units asked engineers for milliseconds while musicians thought in notes. Its inclusion of the reverb figures is the same insight one step removed: a reverb has no repeats to sync, but its pre-delay (the gap before the wash begins) obeys the same grid, and a pre-delay set to a note value lets the dry signal speak in tempo before the room answers.

Worked Example: 120 BPM, the Great Dotted-Eighth Empire

At the default 120 BPM the beat is 500.0 ms, and the table reads like a hall of fame: quarter 500.0, eighth 250.0, sixteenth 125.0, the dotted eighth 375.0 ms — the single most consequential delay time in guitar music, the engine of The Edge’s arpeggios, where a guitarist plays eighths and the delay answers dotted eighths so the combination pours out sixteenths. Triplet quarter (333.3 ms) powers the swung echoes of dub and the loping repeats in half of hip-hop’s sampledelia, and the half note’s full second is the dub-techno cavern. The figures also expose tempo’s leverage: at 128 BPM every value shrinks by 6.25% (the dotted eighth to 351.6 ms), which is why a delay programmed for one song fights the next — the grid moved, and only re-running this arithmetic moves the echo with it.

Pre-Delay: The Reverb’s Courtesy Pause Explained

Reverb’s intelligibility trick deserves its mechanics: without pre-delay, the wash begins the instant the voice does, and the ear — which localises and parses by first arrivals — hears mush. Insert a gap (the note suggests the sixteenth’s figure, 125 ms at the default tempo, with an eighth’s 250 as the lush extreme) and the dry syllable lands, is understood, and then the room blooms behind it: clarity and size simultaneously, from one delay line. The grid-sync matters here too — a pre-delay that is a note value makes the bloom arrive on rhythm, so the reverb breathes with the track instead of behind it. Studios arrived at these figures by ear over decades; the calculator simply discloses that the ear was doing arithmetic: every beloved setting is a note value wearing milliseconds.

Slapback: The Glorious One-Repeat Ancestor

Before tempo sync there was slapback — a single repeat, 100–200 ms, no negotiation with the grid — the sound of Sun Studio and early rock and roll, made by a second tape machine’s fixed geometry rather than by arithmetic. Its time is a distance (tape path length over speed), not a note value, and at many tempos it sits defiantly between the calculator’s fractions: that slight rhythmic wrongness is precisely its swagger, the echo of a voice in a tiled room rather than of a rhythm section. The modern producer chooses slapback deliberately, in full knowledge of the synced alternatives this page tabulates — which is the correct relationship between craft and calculator: the table defines the grid so that departing from it becomes an audible decision instead of an accident. History’s happiest accidents, examined closely, usually had the grid available and declined it on purpose. Slapback’s modern survival — in rockabilly revivals, in lo-fi hip-hop, in any mix that wants its echo to sound like a room instead of a rhythm — is the proof that a calculator’s highest use is sometimes to tell you exactly what you are gloriously ignoring.

Ping-Pong Echoes and the Stereo Field

One more citizen of the table deserves naming: the ping-pong delay, which alternates its repeats between left and right channels — almost always at the eighth or dotted-eighth figure from this page, so the stereo image itself starts keeping time. The arithmetic doubles in apparent complexity and not at all in fact (each channel simply hears every other repeat of the same synced stream), but the perceptual result is a rhythm section with width, a favourite of headphone-era production. It illustrates the table’s deeper use: the figures are not merely settings but compositional choices — which note value will the echo play, in which speaker, against which part — and a calculator that prints all the values at once turns a plug-in’s parameter dive into a menu a musician can read at the speed of thought.

Related Tools and Calculators

More from the Other Calculators hub: the Music Duration Calculator — the same BPM, spent on whole pieces — and the Chord Calculator for what the echoes should repeat.

Frequently Asked Questions, Answered

What delay time should I start with on vocals, then?

The quarter note (500 ms at 120 BPM) at low feedback and low mix is the profession’s default sketch — a slap of space that reads as size without announcing itself — with the eighth (250 ms) for tighter, rhythmic parts and the dotted eighth reserved for when the echo is meant to be heard as an instrument. The calculator gives the figures; the discipline is to choose the note value whose rhythm flatters the phrasing, then set feedback so the repeats die inside two bars. An echo that outlives its welcome is a mixing error regardless of sync; sync merely ensures it is a punctual one.

What does feedback do, and how much is right, exactly?

Feedback routes the delayed signal back into the delay, so each repeat spawns a quieter one: at f fraction returned, repeats decay geometrically (the same mathematics as this hub’s other decays), and the count of audible repeats scales with the tempo-synced time the calculator prints — a 500 ms delay at high feedback fills bars. Dub and ambient styles push feedback toward self-oscillation as a texture; pop keeps it so two or three repeats are audible. There is no universal figure because feedback is denominated in repeats-per-phrase, and the calculator’s times are the denominator of that judgment.

Why do dotted rhythms feel like galloping horses?

Because a dotted eighth against straight eighths interlocks into a stream of sixteenths with a limping accent pattern — long-short-long-short — that the ear groups as momentum (the same figure drives the William Tell overture’s charge and half of Celtic fiddling). The delay trick industrialises it: one played part plus one dotted repeat equals a two-part rhythm section, synchronised by arithmetic rather than by a second musician. The calculator’s dotted column is therefore not an ornament but a rhythm generator, and its 375 ms at the default tempo is, note for note, the most imitated guitar sound of the last forty years.

Does tempo sync matter for reverb decay time too, though?

Loosely: engineers often set the decay (RT60) so the tail dies by a musically sensible boundary — under the next phrase, or across exactly one or two bars — which the hub’s Music Duration arithmetic can price (a bar at 120 BPM in 4/4 is 2 seconds; a two-bar tail is a 4-second reverb, cathedral territory). It is a guideline of the tidy-minded school rather than a law — plenty of beloved records drown in unsynced wash — but the calculator’s figures give even the drowning a grid to be measured against, and pre-delay, the section above argues, is where sync genuinely earns its keep.

What about analogue and tape delays that drift deliciously?

They drift gloriously, and the drift is the point: a tape echo’s time wanders with the machine’s speed stability, so its repeats sit near — never on — the grid, producing the chorus-like warmth that plug-ins now emulate with modulation knobs. The calculator prints the ideal the tape approximates; knowing the exact figure is what lets an engineer decide whether a given unit’s wander is character or malfunction. Perfection is a reference, not a commandment, and this page is content to be the reference — the grid against which even glorious imperfection is measured.

How do I convert a delay in ms back to a note value, then?

Divide by the beat: note value = delay ÷ (60,000 ÷ BPM). A 300 ms echo at 100 BPM (beat 600 ms) is exactly a half-beat — an eighth note — which is the reverse-engineering engineers do when recreating a reference track’s sound from a measured repeat. The calculator’s table makes the lookup instant at any tempo, and the habit — measure, divide, name the note value — is the whole of delay archaeology: classic records’ echoes resolve, almost without exception, into the same dozen fractions of the beat. An engineer who can do this by ear has, in effect, memorised this page; the page exists so the rest of us can rent the skill by the lookup. And once the fractions are named, recreating a reference sound stops being archaeology and becomes transcription — the echo’s rhythm copied as faithfully as its notes.