Calculating MS from BPM
A song’s tempo is usually expressed in terms of beats per minute (bpm). But figuring out a song’s tempo by counting beats for 60 seconds isn’t especially practical. A more efficient way is to find a smaller multiple of 60 and use that as the basis for your calculations. For example, you can count how many beats go by in 15 seconds and multiply that by 4 (15 x 4 = 60 seconds or one minute) or you can count how many beats go by in 10 seconds then multiply that by 6. It can be hard to get a really accurate reading with this approach, but it will get you in the ballpark, if you’re in a pinch.

However, while most musicians think of tempo in terms of bpm, most delay units represent delay time as milliseconds (ms). Studio guitarists used to carry conversion charts in their gigbags to make sure they could always lock in with tempos at a session, and we’re including one for you below. If you ever find yourself in need of a beat-matched delay but don’t have this chart handy, you can use some basic formulas to convert the desired bpm into ms and set your delay accordingly. The basis for the formulas is the number 60,000—the number of milliseconds in a minute. To convert bpm to ms, the formula is:

60,000/bpm = quarter-note ms

For example, 60,000/100 bpm = 600 ms. If you’re playing to a track that is 100 bpm, you’ll need to set your delay at 600 ms to get quarter-note repeats.

To get smaller subdivisions of the quarter note, there are two approaches. You can divide the quarter-note ms reading proportionately, as needed. For repeats in eighth-notes, divide the quarter-note ms by 2, and for repeats in 16ths, divide the quarter-note ms by 4. At a tempo of 100 bpm, quarter-note repeats are 600 ms, eighth-note repeats are 300 ms, and 16th-note repeats are 150 ms.

Or you can use these formulas:

30,000/bpm = eighth-note ms

15,000/bpm = 16th-note ms

For triplet-based music, the formula is:

40,000/bpm = quarter-note-triplet ms

For example, 40,000 divided by 100 bpm = 400 ms. You can divide the quarter-note-triplet ms reading to get values for eighth- and 16th-note triplets. To get eighth-note-triplet repeats, divide the quarter-note-triplet ms by 2, and to get 16th-note-triplet repeats, divide the quarter-note-triplet ms by 4. At a tempo of 100 bpm, quarter-note-triplet repeats are 400 ms, eighth-note-triplet repeats are 200 ms, and 16thnote- triplet repeats are 100 ms.

Or you can use these formulas:

20,000/bpm = eighth-note-triplet ms

10,000/bpm = 16th-note-triplet ms

To calculate ms for dotted-eighth-note rhythmic repeats, the formula is:

45,000/bpm = dotted-eighth-note ms

For example at 100 bpm, you will need a delay time of 450 ms to get repeats in dotted-eighth-notes.