Reverb & Delay Time Calculator
Calculate tempo-synced delay times and reverb decay lengths in milliseconds based on BPM, note value, feedback, and room size. Essential for producers and engineers locking effects to the groove of a track.
About this calculator
Syncing delay and reverb to tempo ensures effects feel rhythmically cohesive rather than cluttered. The base delay time for a given note value is: delay_ms = (60,000 / BPM) × noteValue, where 60,000 converts beats per minute to milliseconds per beat and noteValue is a multiplier (e.g. 1 for a quarter note, 0.5 for an eighth note). This calculator then extends that to account for feedback and room size: effective_time = delay_ms × (1 + (feedback / 100) × (roomSize / 100)). Feedback controls how many repeats occur before the echo fades; room size scales the overall decay envelope. A dotted eighth note delay (noteValue = 0.75) at 120 BPM gives 375 ms — a classic rhythmic effect used across pop, rock, and electronic music. Matching reverb pre-delay to tempo keeps transients clear while the tail fills the space musically.
How to use
Track tempo = 120 BPM, note value = 0.5 (eighth note), feedback = 30%, room size = 50. Step 1: Base delay = (60,000 / 120) × 0.5 = 500 × 0.5 = 250 ms. Step 2: Apply feedback and room size modifier: effective = 250 × (1 + (30/100) × (50/100)) = 250 × (1 + 0.15) = 250 × 1.15 = 287.5 ms. Set your delay plug-in to approximately 288 ms — or use the tempo-sync option and select a straight eighth note — for a rhythmically locked echo that sits cleanly in the mix.
Frequently asked questions
What delay time should I use for a dotted eighth note at 120 BPM?
At 120 BPM, one quarter note lasts 500 ms. A dotted eighth note is 1.5 times an eighth note, and an eighth note is half a quarter note (250 ms), so a dotted eighth = 250 × 1.5 = 375 ms. This delay time is one of the most popular in modern production because it creates a syncopated, cascading echo that fills rhythmic gaps without clashing with downbeats. The U2 guitarist The Edge famously popularised this technique in the 1980s, and it remains a staple in pop, indie, and electronic music production.
How does delay feedback percentage affect the number of audible repeats?
Feedback controls how much of the delayed signal is fed back into the delay input, determining how long echoes continue. At 0% feedback there is only one repeat; at 50% each repeat is half the level of the previous, giving roughly 3–5 audible echoes before fading below perception. At 90% feedback, echoes sustain much longer and can build into a washy, ambient texture. Feedback above 99% can cause runaway self-oscillation — an intentional effect in some electronic music but destructive to a mix if uncontrolled. For clean, rhythmic delay effects in a mix, 20–40% feedback is a common starting range.
Why is it important to sync reverb pre-delay time to the song's BPM?
Pre-delay is the gap between the dry signal and the onset of the reverb tail. Setting it to a musically related time — typically an eighth or sixteenth note at the track's BPM — preserves the clarity and attack of the source instrument before the reverb washes in, preventing the mix from sounding muddy or undefined. For example, at 120 BPM, a 125 ms pre-delay (one sixteenth note) lets the vocal transient cut through cleanly before the reverb tail envelops it. This technique is especially important for lead vocals, snare drums, and any element that needs presence and intelligibility in a dense arrangement.