Polyrhythm Calculator

Free tool to calculate polyrhythms in milliseconds and export them as MIDI. No sign-up

Type how many hits each rhythm has in one cycle, or load a preset like 3 against 4. Leave the third rhythm at 0 if you only need two.
Set the tempo in BPM and how many beats the cycle lasts: 4 beats is one bar of 4/4.
Read the timeline and the numbers: the hit times in milliseconds, where the rhythms meet and the shared grid.
Press Play to hear the loop, and change the values to hear how the pattern shifts.
Download the cycle as a MIDI file for your DAW, save the hit times as CSV, or copy them as text.

Each number is how many equally spaced hits that rhythm has in one cycle. Dashed lines mark the points where all the rhythms hit together. The tempo equivalent is the BPM a metronome would need to click each rhythm on its own.

Nothing is saved or uploaded: everything stays in your browser. Download or copy your results before closing the page. The MIDI file holds one cycle, with each rhythm on its own drum note (C1, D1 and F#1) and the tempo included. Keep this page in the foreground while playing for steady timing.

How do you calculate a polyrhythm like 3 against 4, and when do the two rhythms meet again?

A polyrhythm fits different numbers of equally spaced hits into the same cycle. Divide the cycle length by each number to get the gap between hits: in a 4-beat bar at 120 BPM (2000 ms), 3 against 4 gives hits every 666.7 ms and every 500 ms. The rhythms coincide only at multiples of the cycle divided by the greatest common divisor of the two numbers: for 3:4 that is once per cycle, at the start, while 4:6 meets twice. The shared grid has as many steps as the least common multiple, 12 for 3:4. This free calculator gives you every hit time in milliseconds, plays the loop and exports it as a MIDI file.

What is a polyrhythm?

A polyrhythm is two or more rhythms played at the same time, each dividing the same stretch of time into a different number of equal parts. Tap three even hits with one hand and two with the other over the same bar: that is 3 against 2, the sound of a hemiola. Because 3 and 2 share no common factor, the hits only land together at the start, and the rest of the time they pull against each other, which creates the tension and groove that make polyrhythms interesting. This tool shows exactly when each hit happens, so you can program it in a DAW, a drum machine or a sampler, or practise it by ear.

Made by Luca Martone, sound designer and live sound engineer based in Turin.
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