acalculator

What reverb time fits my tempo?

Type the tempo of your song in beats per minute and pick how long the reverb should last. The calculator gives a pre-delay and a decay time in milliseconds, so the reverb tail ends in time with the beat.

Your numbers

Reverb length
Note feel
Pre-delay
Decay time
968.75 ms

At 120 BPM, set a pre-delay of 31.25 ms and a decay of 968.75 ms.

Pre-delay
31.25 ms
Total reverb time
1,000 ms
One beat
500 ms
Decay for each length
1 bar: 1,968.75 ms; 1/2 note: 968.75 ms; 1/4 note: 468.75 ms; 1/8 note: 218.75 ms

Decay time: 968.75 ms. At 120 BPM, set a pre-delay of 31.25 ms and a decay of 968.75 ms.

How to calculate

Works out reverb pre-delay and decay times in milliseconds that fit a song’s tempo in BPM, for a bar, half note, quarter note or eighth note, straight, dotted or triplet.

Example with the default inputs (Tempo (BPM) 120, Reverb length 1/2 note (room), Note feel Straight, Pre-delay 1/64 note): At 120 BPM, set a pre-delay of 31.25 ms and a decay of 968.75 ms.

Method: Beat = 60,000 ÷ BPM ms; total = beat × beats in the length × feel (1, 1.5 dotted, 2/3 triplet); pre-delay = beat × 4 ÷ N for a 1/N note; decay = total − pre-delay.

  • The beat is a quarter note and a bar is four beats, as in 4/4 time.
  • Pre-delay plus decay fill the chosen musical length, so the tail ends on the beat.
  • The pre-delay keeps its straight length; the feel changes only the reverb length.

Machine-readable copies: Markdown, JSON.

Worked examples

Each example is checked against the calculator on every build.

  1. Tempo (BPM) 120, Reverb length 1/2 note (room), Note feel Straight, Pre-delay 1/64 note gives One beat 500 ms, Pre-delay 31.25 ms, Total reverb time 1,000 ms, Decay time 968.75 ms.Source: TuneLens, Reverb Time Calculator (pre-delay about a 1/64 note; decay = the musical length less the pre-delay; a bar of 4/4 is 240,000 ÷ BPM ms), https://tunelens.com/reverb-time-calculator.html (retrieved 2026-10-03); SI Brochure (BIPM, 9th edition, 2019), Table 8: 1 min = 60 s
  2. Tempo (BPM) 90, Reverb length 1 bar (hall), Note feel Dotted, Pre-delay 1/128 note gives One beat 666.67 ms, Total reverb time 4,000 ms, Pre-delay 20.83 ms, Decay time 3,979.17 ms.Source: TuneLens, Reverb Time Calculator (pre-delay about a 1/64 note; decay = the musical length less the pre-delay; a bar of 4/4 is 240,000 ÷ BPM ms), https://tunelens.com/reverb-time-calculator.html (retrieved 2026-10-03); SI Brochure (BIPM, 9th edition, 2019), Table 8: 1 min = 60 s
  3. Tempo (BPM) 128, Reverb length 1/4 note (tight), Note feel Triplet, Pre-delay None gives Total reverb time 312.5 ms, Decay time 312.5 ms, Pre-delay 0 ms.Source: SI Brochure (BIPM, 9th edition, 2019), Table 8: 1 min = 60 s

How it works

  • One beat (a quarter note) = 60,000 ÷ BPM ms.
  • Total reverb time = beat × beats in the length × feel. A bar is 4 beats, a 1/2 note 2, a 1/4 note 1, a 1/8 note 0.5. The feel is 1 (straight), 1.5 (dotted) or 2/3 (triplet).
  • Pre-delay = beat × 4 ÷ N for a 1/N note: a 1/32 note is beat ÷ 8, a 1/64 note beat ÷ 16, a 1/128 note beat ÷ 32, or 0 for none. The pre-delay is always straight.
  • Decay = total − pre-delay.

Every time is worked out exactly from the typed tempo and shown in milliseconds with 2 decimals, halves rounded up. The table gives the decay for all four lengths with the same feel and pre-delay.

Rules

  • The tempo is 1 to 1,000 BPM.
  • This page is one use of the BPM calculator, which finds the tempo itself and the length of each note.

Worked examples by hand

120 BPM, 1/2 note, straight, 1/64 pre-delay. Beat 60,000 ÷ 120 = 500 ms. Total 2 × 500 = 1,000 ms. Pre-delay 500 ÷ 16 = 31.25 ms. Decay 1,000 − 31.25 = 968.75 ms.

90 BPM, 1 bar, dotted, 1/128 pre-delay. Beat 60,000 ÷ 90 = 666.67 ms. Total 4 × 1.5 × 666.67 = 4,000 ms. Pre-delay 666.67 ÷ 32 = 20.83 ms. Decay 4,000 − 20.83 = 3,979.17 ms.

128 BPM, 1/4 note, triplet, no pre-delay. Beat 60,000 ÷ 128 = 468.75 ms. Total 468.75 × 2/3 = 312.5 ms, all of it decay.

Other questions people ask

How do I time reverb to the tempo?

Work out one beat in milliseconds, 60,000 ÷ BPM, and pick a musical length for the whole reverb, such as a half note (2 beats). Take off a short pre-delay and set the rest as the decay. At 120 BPM a half note is 1,000 ms; with a 31.25 ms pre-delay, the decay is 968.75 ms.

What is reverb pre-delay?

The gap between the dry sound and the start of the reverb. A short pre-delay, often about a 1/64 note, keeps the start of each note clear before the reverb fills in behind it.

Which reverb length should I pick?

A bar suits a large hall or a slow ballad, a half note a room, and a quarter or eighth note a tight ambience on drums or fast parts. Try the length that leaves space before the next hit.

What do dotted and triplet mean here?

A dotted length is 1.5 times the straight one; a triplet length is 2/3 of it. Use them when the song swings or the part plays in triplets.

Is the decay time the same as RT60?

Many plugins set decay as the time for the reverb to fade by 60 dB (RT60), others to silence. Either way, a tempo-based value is a starting point; trust your ears.