About tempo and BPM
Tempo is the speed of a piece of music, measured in beats per minute (BPM). A higher BPM means a faster pulse. This tool converts a BPM value into the length of each note in milliseconds (ms), which is the practical number you need for setting a metronome, dialling in delay and reverb times, programming an LFO, or beatmatching two tracks. Enter a tempo and it returns quarter, eighth, sixteenth, and triplet durations at once.
Before the metronome, tempo was described with Italian words that convey feel as well as speed: Largo (broad and slow), Adagio (at ease), Andante (walking pace), Moderato (moderate), Allegro (lively), and Presto (very fast). Maelzel's metronome, patented in 1815, let composers attach an exact BPM to those markings, which is why scores often read "Allegro, quarter note = 132."
BPM also defines genre. House music lives at roughly 120 to 128 BPM, techno at 125 to 150, hip-hop often at 85 to 95, and drum and bass near 170 to 175. DJs beatmatch by nudging two tracks to the same BPM so their beats align; producers sync time-based effects to the tempo so echoes land musically rather than randomly.
How it works: the formula
A quarter note is one beat, and there are 60,000 milliseconds in a minute, so the quarter-note length is simply 60,000 divided by the BPM. Every other note value is a fraction or multiple of that:
quarter_ms = 60000 / BPM eighth_ms = quarter_ms / 2 sixteenth_ms = quarter_ms / 4 half_ms = quarter_ms x 2 whole_ms = quarter_ms x 4 triplet_8th = quarter_ms / 3 dotted_note = base_note x 1.5
- 60000 = milliseconds per minute (60 seconds x 1000).
- BPM = beats per minute, assuming the beat is a quarter note (the usual case in 4/4).
- Dotted notes add half their value again (x 1.5); triplets divide a beat into three.
- Frequency in Hz, if needed, is BPM / 60 (beats per second).
Worked example: delay times at 120 BPM
Suppose your track is at 120 BPM and you want a delay synced to the eighth note.
- Quarter note: 60000 / 120 = 500 ms.
- Eighth note: 500 / 2 = 250 ms.
- Sixteenth note: 500 / 4 = 125 ms.
- Dotted eighth (a classic delay setting): 250 x 1.5 = 375 ms.
- Classification: 120 BPM sits at the Moderato / Allegro border.
Reference table: tempo markings and beat length
| Marking | BPM range | Quarter note (ms) | Feel |
|---|---|---|---|
| Largo | 40-60 | 1500-1000 | Very slow, broad |
| Adagio | 66-76 | 909-789 | Slow, at ease |
| Andante | 76-108 | 789-556 | Walking pace |
| Moderato | 108-120 | 556-500 | Moderate |
| Allegro | 120-168 | 500-357 | Fast, lively |
| Presto | 168-200 | 357-300 | Very fast |
Common pitfalls
- Assuming the beat is always a quarter note. In 6/8 or 12/8 the beat is usually a dotted quarter; the 60000 / BPM formula still gives the quarter-note length, so adjust if your meter counts a different unit as the beat.
- Confusing half-time and double-time. A 170 BPM drum-and-bass track is often felt as 85 BPM half-time. Both are correct; pick the one your delay or sequencer expects.
- Rounding delay times too hard. 500 ms is exact at 120 BPM, but 130 BPM gives 461.5 ms; rounding to 460 introduces audible drift over a long passage. Keep the decimals when precision matters.
- Mixing dotted and triplet feels. A dotted eighth (x 1.5) and an eighth triplet (divide by 3) are different rhythms; using the wrong one makes a synced delay sound off.
- Forgetting tempo can drift. Live or hand-played recordings rarely hold a perfectly fixed BPM, so a single calculated delay time may need tweaking section by section.