Delay Time Calculator Guide: BPM, Dotted Notes and Triplets
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A delay sounds locked to a song when each repeat lands on a note value at the song’s tempo. The math is simple once you know one number: how long a quarter note lasts in milliseconds.
The Core Formula
Quarter note (ms) = 60,000 / BPM
A minute has 60,000 milliseconds, and this calculator treats BPM (beats per minute) as quarter notes per minute. A score may define a different beat unit, such as a dotted quarter in compound meter; convert that tempo to a quarter-note pulse first. Every other note value comes from the quarter note:
| Note type | Rule | Example formula |
|---|---|---|
| Straight | Halve or double the quarter | Eighth = quarter / 2, half = quarter × 2 |
| Dotted | Multiply by 1.5 | Dotted eighth = eighth × 1.5 |
| Triplet | Multiply by 2/3 | Eighth triplet = eighth × 2/3 |
A dotted note is the note plus half its own length. A triplet fits three notes into the space of two, so each one is two thirds as long.
Worked Example at 120 BPM
- Quarter note: 60,000 / 120 = 500 ms
- Eighth note: 500 / 2 = 250 ms
- Dotted eighth: 250 × 1.5 = 375 ms
- Eighth triplet: 250 × 2/3 = 166.67 ms
Here is the full set at the same tempo:
| Note value | Straight | Dotted | Triplet |
|---|---|---|---|
| Half | 1000 ms | 1500 ms | 666.67 ms |
| Quarter | 500 ms | 750 ms | 333.33 ms |
| Eighth | 250 ms | 375 ms | 166.67 ms |
| Sixteenth | 125 ms | 187.5 ms | 83.33 ms |
The dotted eighth is a popular choice for rhythmic patterns, because its repeats fall between the straight eighth notes you play. If your pedal only accepts whole numbers, round to the nearest millisecond.
To work out a different tempo, repeat step 1 with the new BPM and apply the same rules. At 90 BPM, for example, the quarter note is 60,000 / 90 = 666.67 ms, so the dotted eighth is 666.67 / 2 × 1.5 = 500 ms.
Delay Time vs Modulation Rate
Some pedals and plugins show a rate in Hz (hertz, or cycles per second). The length of one cycle, called the period, is the reciprocal: period = 1 / Hz. A 2 Hz rate has a period of 0.5 seconds, or 500 ms.
That number is not automatically a delay repeat time. On a chorus, or on the modulation section of a delay, the rate controls how fast the pitch wobbles. Converting it to milliseconds gives you the length of one wobble, not the gap between echoes. Only treat a Hz value as a repeat rate if the manual says that knob sets delay time.
If you do need to convert a delay time into Hz, divide 1000 by the time in milliseconds. A 500 ms delay works out to 2 Hz.
Getting an Accurate BPM
Tap tempo sets the tempo from your taps. It does not listen to a recording or detect a song’s tempo from audio. Good BPM sources include:
- The tempo setting in your recording project
- A metronome you are already playing to
- Steady tapping along with the song over several beats
If you record at home, the project tempo in your recording software is the most dependable number to use. Our guide to recording guitar on a PC covers the interface, track, and monitoring setup. Set your project tempo separately to match the quarter-note BPM used here.
The project tempo works the same way if you record guitar in GarageBand on a Mac. Timing is only part of how a delay sounds, though. A compressor pedal for guitar evens out loud and soft notes and can add sustain. That changes how consistent the notes feeding your timed repeats are.
Using the Calculator
The delay time calculator takes a BPM, typed in or tapped, and gives you straight, dotted, and triplet values, so you do not have to work through the formulas by hand. Copy the millisecond value into your pedal or plugin, then adjust feedback and mix to taste.
