How long is one beat at a given BPM?

One beat lasts 60000 divided by the BPM in milliseconds. At 90 BPM a beat is about 667 ms, so a 4/4 bar is about 2667 ms and a two-bar loop is about 5333 ms long.

Why slice into 8, 16, or 32 equal pieces?

Powers of two line up with the beat grid. Sixteen slices over a one-bar 4/4 loop gives one slice per sixteenth note, so every chop falls on a musical division and stays in time when you rearrange them.

What are the sample numbers for?

Sample-accurate editors and hardware samplers cut at sample positions, not just milliseconds. The tool converts each boundary to a sample index at 44.1 kHz so your cuts land exactly on the grid with no drift.

Does this work for triplet or odd time signatures?

Yes for whole-bar loops. Set the beats per bar to match the meter, such as 3 for 3/4. For triplet chops, set the slice count so it divides the loop into triplet groupings, for example 12 or 24 over a 4/4 bar.

What if my loop is not an exact number of bars?

Then it will not slice cleanly to a tempo grid. Trim or time-stretch the loop to a whole number of bars at the target BPM first, then use this tool to find even, on-grid cut points.

What is the Sample Chop BPM Grid Calculator?

Calculate the exact cut points in milliseconds and samples for dividing a loop into 8, 16, or 32 equal slices at any BPM and bar count. Built for MPC and DAW chop-and-rearrange production workflows. Runs in your browser. It runs free in your browser on Gera Tools, with nothing uploaded.

Sample Chop BPM Grid Calculator

Name: Sample Chop BPM Grid Calculator
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

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Chopping a sampled loop into even slices is the heart of MPC-style production, but the cuts only stay in time if they land exactly on the beat grid. This tool does the arithmetic: enter the tempo, bar count, and how many slices you want, and it prints every cut point in both milliseconds and samples.

How it works

A loop of a whole number of bars at a fixed tempo has an exact length, which divides evenly into equal slices:

beat (ms)   = 60000 / BPM
bar (ms)    = beat × beats per bar
loop (ms)   = bar × bars
slice (ms)  = loop / slice count
boundary i  = i × slice (ms)
sample #    = (ms / 1000) × 44100

Because every boundary is an exact fraction of the loop, the slices line up with the underlying grid, so you can reorder them, drop some, or repeat others and the groove stays locked to the tempo.

Worked example

A two-bar 4/4 loop at 90 BPM:

Beat duration: 60,000 / 90 = 666.67 ms
Bar duration: 666.67 × 4 = 2,666.67 ms
Loop duration: 2,666.67 × 2 = 5,333.33 ms

Sliced into 16 equal pieces, each chop is 5,333.33 / 16 ≈ 333.33 ms. In samples at 44.1 kHz, each slice is 333.33 / 1000 × 44100 ≈ 14,700 samples. This puts every cut exactly on an eighth-note grid — the foundation of a rearranged drum break.

Sliced into 32 pieces instead, each chop is one sixteenth note at this tempo — 166.67 ms — useful for fine-grained rearrangement or stutter effects.

The production workflow

Record or import the loop. Know your source BPM precisely. If the original recording is not perfectly in tempo, time-stretch it first in your DAW before using these cut points.
Calculate the boundaries. Enter the BPM, bar count, and slice count here to get the exact cut points in milliseconds.
Mark the cuts in your DAW or sampler. Most DAWs and hardware samplers accept either millisecond or sample-accurate positions. Use the sample number column for maximum precision.
Load slices onto pads. On an MPC or similar, each pad plays one slice. Reorder, repeat, or mute pads to create a new groove from the chopped material.

Why powers of two?

8, 16, and 32 slices align with musical subdivisions in 4/4 time:

Slices over 1 bar	Musical subdivision
4	Quarter note
8	Eighth note
16	Sixteenth note
32	Thirty-second note

Non-power-of-two slice counts are possible for special effects (triplet chops, polyrhythm work) but will not land on a standard musical grid unless the loop length is carefully chosen to match.

Tips and example

Always trim your source so it is an exact number of bars at the target BPM before slicing; even a few stray milliseconds at the loop point will smear every cut and make the rearranged pattern drift out of time. If you are working with a sample of unknown BPM, find the tempo first using your DAW’s beat detection, then round to the nearest whole or half BPM and set the loop length before chopping.