Tempo and Note Duration Formula
Calculate note duration in milliseconds from BPM: duration = 60,000 / BPM.
Quarter notes, eighth notes, dotted notes — all explained.
The Formula
In music, BPM (beats per minute) describes tempo. Each beat is typically a quarter note. The duration of a quarter note in milliseconds is 60,000 divided by the BPM — because there are 60,000 ms in a minute.
All other note durations derive from the quarter note by multiplication or division:
| Note | Duration relative to quarter note |
|---|---|
| Whole note | × 4 |
| Half note | × 2 |
| Quarter note | × 1 (the beat) |
| Eighth note | × 0.5 |
| 16th note | × 0.25 |
| 32nd note | × 0.125 |
| Dotted quarter | × 1.5 (adds half its value) |
| Dotted half | × 3 |
| Triplet 8th | × 0.333 (3 fit in a quarter) |
This formula is critical for audio production — setting delay times, reverb pre-delays, and LFO rates to tempo-synchronised values creates a cohesive, rhythmically locked sound. A delay set to the dotted eighth note value (375 ms at 120 BPM) is the classic U2/The Edge "ambient delay" sound.
Example 1
At 120 BPM, find the duration of each note value.
Quarter note = 60,000 / 120 = 500 ms
Eighth note = 500 / 2 = 250 ms
Dotted quarter = 500 × 1.5 = 750 ms
Whole note = 500 × 4 = 2,000 ms (2 seconds)
Example 2
Set a guitar delay to dotted-8th at 90 BPM.
Quarter note = 60,000 / 90 = 666.7 ms
Eighth note = 333.3 ms; Dotted-8th = 333.3 × 1.5
Delay time = 500 ms
When to Use It
- Setting delay, reverb, and LFO rates in DAW music production
- Timing animations or visual effects to music
- Music theory and rhythm analysis
- Metronome and practice app development