Broken rice grading, explained
"5% broken", "25% broken", "A1 Super": much of the rice trade prices milled rice by how much of it is broken. The number sounds simple, but it depends on definitions most people never read. Here they are in plain language.
Everything is measured against the whole kernel
Broken rice isn't defined in millimetres. It's defined as a fraction of the average length of a whole kernel of that same rice. That's why the same rule works for a short Japonica and a long Thai jasmine.
ISO 7301 (the international specification for rice) sets the two key lines:
- Whole kernel: at least nine-tenths of the average length.
- Head rice: whole kernels, plus pieces at least three-quarters of the average length.
- Broken kernel: a piece shorter than three-quarters of the average length that doesn't pass a 1.4 mm round-hole sieve.
- Chip: a fragment that passes through the 1.4 mm sieve.
The Codex Alimentarius rice standard (CXS 198) splits the brokens further:
| Piece | Length vs. average whole kernel |
|---|---|
| Head rice | ≥ 3/4 |
| Large broken | 1/2 to 3/4 |
| Medium broken | 1/4 to 1/2 |
| Small broken | ≤ 1/4, but doesn't pass a 1.4 mm sieve |
| Chip | passes a 1.4 mm sieve |
National and contract grades build on these ideas with their own limits and names, so always check which definitions your contract refers to.
Percentages are by weight
A "5% broken" grade means 5% by weight, not 5 grains in 100. Because broken pieces are lighter than whole kernels, the broken share by count is always higher than by weight. A sample with 20% broken pieces by count might be only 10–12% broken by weight. When you compare numbers, make sure both sides mean the same thing.
Why grains break
- Fissuring before milling: paddy that is dried too fast, too hot, or re-wetted after drying develops internal cracks that snap during milling.
- Harvest timing and moisture: very dry or over-mature grain in the field fissures more.
- Immature and chalky grains: chalky, floury kernels are weaker and break more easily.
- Mill settings: aggressive husking or whitening, worn rubber rolls or stones, and running the mill over capacity all raise breakage.
Does broken rice matter for your use?
For table rice, head rice drives price. For products where rice is ground into flour, what matters more may be variety, amylose content, consistency and cleanliness than whether every kernel is whole — but specifications differ by buyer and product, so agree on it in the contract.
How brokens are measured
Laboratories and mills use a sample divider, then separate pieces with indented-cylinder graders or sieves, or by hand, and weigh each fraction. Camera-based grain analysers do the same job by measuring every kernel in an image.
The free rice.ag Grain Scanner applies the ISO/Codex length classes above to a phone photo, and estimates weight shares from each piece's area. It's built for quick, consistent comparisons — lot to lot, supplier to supplier, before and after a mill adjustment — rather than as a replacement for a certified test.
Sources
- ISO 7301:2021, Rice — Specification (definitions 3.10–3.16, 3.26).
- Codex Alimentarius, Standard for Rice, CXS 198-1995.
Published by rice.ag, a free project by Wildfield, rice growers and millers in Fang, Chiang Mai.