Foundational
Coffee grading, system by system
There is no world grade for green coffee. What several national systems count, what a defect and a screen number are, and how far a physical grade predicts the cup.
In short
There is no universal grade for green coffee. The trade's handbook says so in as many words: every producing country has its own classification logic. A grade is an answer to a question, and the questions differ. One country's grade is a count of faulty beans, another's is a size of hole, another's is a height above sea level.
This page sets out what several systems count, using only documents that were read, and says where one was not. Then it takes up the question underneath: how far any physical grade predicts what a coffee tastes like.
Eight things a grade can be made of
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The International Trade Centre's handbook lists the criteria that classification systems draw on: processing method, screen size, number of defects, altitude, density, region, variety and cup quality. No system uses all eight, and a commercial description usually strings several together. Its example from Brazil reads as a sentence once decoded: natural arabica, shipped through Santos, a defect class, a bean size, a cup class.
So the first thing to ask of any grade on a bag is which of those eight it is. A size grade and a defect grade are both real information. They are information about different things.
What each system counts, from the documents read
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A model of how the systems differ, not a full account of any of them. The last column says where each description comes from; where it is the trade handbook's example, the country's own rule was not read.
| Variable | Typical range | What moving it does |
|---|---|---|
| Brazil | Defects, size, colour and cup, each stated separately | The federal regulation of 2003, read for this page: a type from the defects in a 300-gram sample, running from type 2 with four defects to type 8 with 360, beyond which a lot is outside the types; a shape and screen size; one of eight colour classes; and a cup class, seven of them for arabica. It also caps moisture at 12.5 per cent. |
| Kenya | Size, shape and density | Seven letters, E, PB, AA, AB, C, TT and T, as a 2022 study describes them. The handbook adds that cup quality is classed separately and that the best-tasting lots are mostly sold on an actual sample. The Kenyan regulation was not read. |
| Ethiopia | Raw inspection and cup together | As a 2014 study recorded it: the raw bean counted for 40 per cent and the cup for 60, with washed coffee graded 1 or 2 and natural 3 to 5. The system has since been revised and the current rules were not read. |
| Colombia | Size | The handbook's example, supremo 17/18, tolerates at most 5 per cent of beans below screen 17. The federation's export rule was not read. |
| El Salvador and Guatemala | Altitude, then preparation | The handbook describes strictly high grown in El Salvador as above 1,200 metres and strictly hard bean in Guatemala as above 1,400. These are its descriptions; neither country's rule was read. |
| Vietnam | Defects and size | Six grades for robusta, a special grade and grades 1 to 5, on the handbook's account. The national standard was not read. |
| International Coffee Organization target | Defects and moisture only | Resolution 420 of 2004, read in full: not more than 86 defects in 300 grams for arabica or 150 for robusta, and moisture between 8 and 12.5 per cent. Voluntary, and a floor for a certificate mark, not a grade. |
Each row is one document's description of one system at one date. The grades are not rungs on a common ladder: a top grade in a size system and a top grade in a defect system have nothing to be compared by.
European Preparation: one phrase, two sets of numbers
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Preparation terms describe how thoroughly a lot was sorted before export. The handbook gives them in two of its examples, and the two do not match. For El Salvador it describes European Preparation as a maximum of six defects in 300 grams and American Preparation as a maximum of twelve. For Guatemala it describes European Preparation as beans above screen 15 with a maximum of eight defects, and American Preparation as above screen 14 with up to 23.
Both are the handbook's reports of commercial usage, and the lesson is in the mismatch. A preparation term names a tighter and a looser sort within one origin's trade. It is not a number that travels.
What a screen number is
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Size is graded on screens: metal sheets with round holes that hold back beans above a certain size and let smaller ones fall through. The handbook's table gives the hole for each screen number in millimetres as the international standard has it: 4.00 for screen 10, 5.60 for 14, 6.00 for 15, 6.30 for 16, 6.70 for 17, 7.10 for 18 and 8.00 for 20.
Screen numbers are usually explained as sixty-fourths of an inch, and the arithmetic roughly agrees: seventeen sixty-fourths of an inch is 6.75 millimetres against the table's 6.70. The handbook does not state that convention itself.
Two details from the same passage. Peaberries, the single rounded seeds that form when a cherry holds one bean, are taken out on screens with oblong slots, usually 4 or 4.5 millimetres wide. And a screen is not exact: where a contract demands that nothing at all pass a given size, the handbook's suggestion is to open the holes very slightly to allow a tolerance. Its reason for sizing at all is the same as the mill's. Beans of one size roast evenly.
A defect is a convention with a weight
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The FAO's guidelines define defects as the collective name for undesirable particles in bulk green coffee: faulty beans, parts of beans, fruit tissue and foreign matter. They add two things that matter more than the list. The terms are used in some producing countries and not in others, and defects are given a weighted value so that a lot can be classified. Faulty processing, pest damage and bad weather during fruit development are the causes they name.
The handbook sorts defects into primary ones, with a significant effect on the cup, and secondary ones, with a minor effect. Its examples of primary defects are a fully black bean, a fully sour bean, a fermented sour bean, foreign matter such as stones and wood, and dried cherries, each with what it calls a possible effect on taste.
The weights are where systems part. Brazil's regulation counts three shells as one defect, two sour beans as one, and five broken beans as one. An FAO manual written for Laos reproduces an older American specialty classification beside the Brazilian one, and in that account it takes five shells to make a full defect. The International Coffee Organization's resolution contains the same idea in a footnote: for a cultivar that naturally breaks into many pieces, twenty broken beans may count as one defect where five normally would. A defect count is therefore a count under a particular set of weights, and two counts are comparable only if the weights were the same.
The guidelines also give a reason for sorting that has nothing to do with flavour. Results on lower grades indicated that some classes of defect can carry much more ochratoxin A than sound beans. The document is careful to call this far from universal and to ask for more investigation, and it says sorted-out defects should not be blended back into clean coffee unless analysis has shown them acceptable.
The specialty standard, in the version that could be read
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The best-known defect standard among roasters is the green grading protocol of the Specialty Coffee Association. Its current pages returned an error, so what follows is an older text: the protocol its American predecessor published in November 2009, read in full from an archived copy. It is two pages long.
That protocol counts defects in a 350-gram sample. A full defect is either Category 1, the primary kind, or Category 2, and a specialty-grade sample must have no Category 1 defects and no more than five Category 2 defects. Several faulty beans can make up one full defect, and the protocol's own example is five broken beans. A bean with two faults is counted once, as the more serious. The sample must also be blue-green to green in colour and free of foreign smells. The protocol says its classification defines only two grades, specialty and premium, and that anything else is not classified by it.
An FAO manual for Laos reproduces an earlier version still, citing a website: 300 grams, not more than five full defects and no primary ones, no quakers, moisture between 9 and 13 per cent, and at least one distinctive attribute in the cup, with four lower grades beneath. So the same association's standard has been stated on two sample weights. Whether today's association still uses the 2009 text was not checked, and a seller quoting a specialty defect count should be asked which version is meant.
How far a physical grade predicts the cup
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Less far than the names suggest, and the trade's behaviour shows it. The handbook says standard qualities can be traded on description alone, while premium and specialised coffees are mostly sold on sample. Of Kenya, whose letter grades are among the most recognised in the world, it says the top cupping coffees are mostly sold on an actual sample. If a grade settled the question of taste, nobody would need the sample.
The research read for this page does not settle it either. A study in south-western Ethiopia measured bean size, weight, density and counted defects across elevations and production systems. It found fewer defective beans and higher density at higher elevation, with elevation the main influence and the production system second. It tasted nothing, so it shows what moves the physical properties and not whether they predict the cup. CoffeeHQ read no study that tests a national grade against a tasting panel.
A grade is still worth having. It tells a roaster whether the beans will roast evenly and how carefully the lot was sorted. It was designed to answer those questions.
Four systems described where they are used
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- Brazil — A regulation that states defects, size, colour and cup separately, with cup classes named for softness and for a medicinal taint.
- Kenya — Seven letters for size, shape and density, taking no account of the variety the beans came from.
- Ethiopia — A grade that, as one study recorded it, also told you whether the coffee was washed or natural.
- Colombia — Size names whose export definition CoffeeHQ has read only at second hand, and says so.
What is not claimed here
CoffeeHQ explanation
No national regulation other than Brazil's was read. The descriptions of Kenya and Ethiopia come from studies; those of Colombia, Central America and Vietnam are the trade handbook's examples of commercial usage and may not match the current rule in each country.
The Specialty Coffee Association's current standard and the international standards for defects and size analysis were not opened. The specialty figures above are those of a 2009 protocol and of an older account, and are dated as such.
This page does not rank the systems, and it does not say which grade to buy. It gives no figure as a mark of quality.
What to do next
- Green coffee: what it is and how it is judged — The assessment a grade is one part of: moisture, water activity, samples and what lot terms mean.
- Origin and traceability terms — The other words on a bag, which are about where a coffee came from and not how it was sorted.
- Coffee authenticity and fraud — What happens when a description says more than the lot can support, and how it is detected.
- Coffee Expert, level 6: green coffee — A lesson built on these pages, with an exercise in reading two origins' grade names side by side.