The formula
One beat (a quarter note in 4/4) lasts 60,000 ÷ BPM milliseconds. At 120 BPM that's 500 ms. Every other note length comes from there:
- Half it for an eighth note (250 ms at 120), halve again for a sixteenth (125 ms).
- Multiply by 1.5 for a dotted note. A dotted eighth at 120 BPM is 375 ms.
- Multiply by ⅔ for a triplet. An eighth-note triplet at 120 BPM is 166.67 ms.
- Hz is 1000 ÷ ms. Use it to sync an LFO or tremolo that only takes a rate in hertz.
Going the other way, BPM = 60,000 ÷ beat length in ms. If a delay pedal shows 375 ms and you know it's set to quarter notes, the song is at 160 BPM.
Setting delay and reverb to the tempo
A delay that matches the beat sits inside the groove instead of blurring it. Quarter-note and eighth-note repeats are the safe starting points. The dotted eighth is the one that makes a single guitar line sound like two interlocking parts, a sound that defined a lot of 80s rock and plenty of worship music since.
For reverb, try setting the pre-delay to a 1/64 or 1/32 note so the dry hit comes through before the tail, then trim the decay so it fades out before the next snare. At 120 BPM a quarter note is half a second, so a decay of about 1.5 seconds lands on the next downbeat of a 4/4 bar.
Samples per beat
If you're slicing loops or writing audio code, multiply the milliseconds by your sample rate in kHz. One beat at 120 BPM is 500 ms, which is 22,050 samples at 44.1 kHz or 24,000 samples at 48 kHz.
Questions
What is 1/4 at 120 BPM in ms?
500 ms. A quarter note is one beat, and one beat at 120 BPM is 60,000 ÷ 120 = 500 ms.
What is a dotted 1/8 delay at 128 BPM?
351.56 ms. A quarter note at 128 BPM is 468.75 ms, an eighth is 234.38 ms, and dotted means 1.5 times that.
Don't know the BPM of the song?
Tap it in first. The tap tempo page shows the same delay table under the pad for whatever you tap.
Can I share a result?
Yes. The address bar updates as you type (for example tempos.cc/bpm-to-ms?bpm=95), so you can copy the link or bookmark a tempo you use often.