What is a polyrhythm?

A polyrhythm is the simultaneous use of two or more rhythmic patterns that divide the same time span into different equal divisions. A 3:4 polyrhythm, for example, plays 3 evenly spaced beats against 4 evenly spaced beats in one measure.

What does LCM cycle mean?

LCM stands for Least Common Multiple. When two patterns have beat counts of 3 and 4, the LCM is 12. That means the full polyrhythm cycle takes 12 pulse units before both patterns land on beat 1 at exactly the same time.

How is note duration calculated?

One measure duration in milliseconds = (60 / BPM) × beats_per_measure × 1000. Each pattern's note duration = measure_ms / beat_count. For example, at 120 BPM with a 4-beat measure (2000 ms), a pattern of 3 notes gives 2000/3 ≈ 666.7 ms per note.

Can I add more than two patterns?

Yes. Use the "+ Add Pattern" button to add a third or fourth voice. The LCM and grid update for all patterns simultaneously.

What is the difference between polyrhythm and polymeter?

Polyrhythm fits multiple beat counts into the same measure length. Polymeter uses different time signatures that cycle at their own pace, so measures are the same length but bar lines fall at different points.

Polyrhythm Calculator

Name: Polyrhythm Calculator
Availability: InStock
Author: Nham Vu

Enter two or more beat counts and a tempo to see note durations, LCM cycle length, and a visual grid of where beats align.

Settings

Tempo (BPM)

Measure pulse (beats)

Summary

Enter two or more beat counts and a tempo to see note durations, LCM cycle length, and a visual grid of where beats align.

How it works

Each pattern fills one measure. Enter how many evenly spaced beats each pattern has (e.g. 3 and 4 for a 3:4 polyrhythm).
Set the tempo in BPM and select the measure length (quarter-note or eighth-note pulse).
The calculator divides the measure duration by each beat count to get each note's duration in milliseconds.
It then finds the Least Common Multiple (LCM) of all beat counts, which tells you how many measures pass before every pattern lands on beat 1 at the same time.
A visual grid plots each pattern's beat positions across one full LCM cycle so you can see coincidences and offsets at a glance.

Use cases

Understand where beats align in a 3-against-4 or 5-against-7 polyrhythm before performing or programming it.
Calculate exact note durations (ms) to configure drum machine step lengths or DAW grid snapping.
Find the LCM cycle so you know how many bars to loop a polyrhythmic pattern before it resolves.
Study cross-rhythm structures when arranging for multiple percussion voices.
Teach polyrhythm concepts visually in music theory or composition classes.

Frequently Asked Questions

Last updated: 2026-07-01 · Reviewed by Nham Vu