Specialty Coffee Wiki

Kenya AA

Properties3
descriptionThe most famous two letters in African coffee, and what they actually measure — a bean size, not a farm, a variety or a flavour. How Kenya's grade ladder works, why AA fetches a premium anyway, and how much of the published detail turns out to be trade convention rather than law.
tagsconcept, grading, kenya, green-coffee, auction, quality
aliasesKenyan coffee grades, Kenya coffee grading, Kenya grade letters, Kenya AB, Kenya TT, Kenya MH/ML, AA grade coffee

11 min read

Kenya AA

“Kenya AA” is a shoe size. It is written on bags and menus as if it were a quality mark, and it sells at a premium as if it were one, but the two letters describe exactly one thing: how big the beans are. Not the farm, not the plant, not the cup. A brilliant coffee and a mediocre one grown on the next hill can both be AA, and frequently are.

It is on this wiki as a concept rather than a place because that is what it is — the top rung of Kenya’s national size ladder, catalogued at the Nairobi Coffee Exchange auction and inherited by every roaster who buys from it.

What it measuresBean size, by screen
The screenPasses screen 18, held by screen 1712
Roughly7.2 mm across3
Size tolerance5% of beans may sit above or below the stated screen1
Where it is usedKenya’s grade system, catalogued at the Nairobi Coffee Exchange
Equivalent elsewhereSupremo in Colombia; “AA” is the African convention for the same idea4
What it does not tell youVariety, farm, altitude, processing, cup score

What the letters mean

Kenyan green coffee is sorted at the dry mill by shaking it through a stack of perforated screens, each numbered in sixty-fourths of an inch — the same mechanical sizing described under Green coffee grading and Dry milling. AA is the fraction that falls through the screen with 18/64-inch holes and is caught by the 17/64-inch one: about 7.2 mm in diameter, the largest of the normal grades.123

The tolerance matters as much as the number. Grades AA, AB and PB are allowed up to 5% of beans above or below the screen size on the label, so “AA” is a promise with a stated margin rather than a description of every bean in the bag.1

Kenya uses eight grade names in its auction catalogue, and only the first four are ones a specialty drinker is likely to see:256

GradeWhat it is
EElephant — the giants, often two beans fused into one
PBPeaberry — a single round seed instead of the usual flat-sided pair
AAThe largest standard grade, screen 17–18
ABThe workhorse: screen 16–17, the bulk of the crop1
CSmaller than AB
TTThe lightweights pulled out of AA and AB — right size, wrong density
TThe smallest, plus broken fragments
MH / MLMbuni Heavy / Mbuni Light — dried-in-the-cherry coffee, the bottom of the sheet

TT is the one that gives the game away. If size were the whole story there would be no need for it — TT exists precisely because some AA-sized beans are too light to be any good, so they are blown out and sold separately. Kenya grades by screen size and by density, and only then does anyone taste anything: lots are cupped by national graders after they are sized, not before.4

To verify — the screen numbers for the minor grades do not agree

The AA definition (through 18, held by 17) is consistent across sources.12 Below it, the published figures fall apart. Trabocca puts PB at “screen size 12+” and AB at 16/17;1 a Kenyan producer’s guide puts PB at “size 17”, AB at 6.8 mm / size 16–17, E at “size 21+”, C at 12–14, TT at “16–20” and T under 12.3 TT spanning 16–20 cannot be reconciled with TT being a low-density byproduct of AA and AB, and the two PB figures are not close. Separately, Perfect Daily Grind describes the very large African “AA” bean as 19–20/64 inch, which is E territory in the other sources.4 Treat AA = 17/18 as solid and every other screen number on this page as trade convention that no two sources state the same way.

To verify — no Kenyan legal text was located

Sources routinely describe Kenyan grading as statutory: one producer page calls it “a policy by law and a Kenya Auction requirement” without naming the instrument,3 and Trabocca attributes the standards to “the Kenyan Department of Agriculture, Coffee Directorate and the Nairobi Coffee Exchange.”1 Neither a Kenyan statute nor a Coffee Directorate grading regulation was read here — the Agriculture and Food Authority’s coffee page returned no usable text to an automated request. This wiki’s Kenya and Nairobi Coffee Exchange notes already record the same gap: the grade letters are certain, the published definitions are conventional, and no government grading manual has been found. Do not quote any screen figure here as law.

Why it sells for more anyway

If AA measures size, why does the market pay for it?

Three reasons, in descending order of honesty.

  1. Roasting consistency. A batch of uniformly large beans browns evenly. Mixed sizes do not — the small ones scorch while the large ones lag. Size grading exists to solve a roasting problem before it is anything else.2
  2. Size correlates loosely with growing conditions. Slow, cool ripening at altitude tends to produce bigger, denser seeds, so a high proportion of AA is weak evidence about where and how the coffee grew. Weak, not strong — see Terroir.
  3. It is the label buyers already know. “Kenya AA” has ninety years of shelf equity. That is a marketing fact, not a quality one.

The trade’s own literature is unusually blunt that step three has outrun the others. Trabocca states outright that larger sizes do not guarantee superior flavour, and Perfect Daily Grind that “some people have adopted a general view that larger beans are better beans. But this [is] not accurate” — recommending buyers “dig a little deeper and perform some cuppings.”14

This is the same warning Green coffee grading gives about screen size generally, and it is why serious buying in Kenya has moved toward the post-2006 direct window, where a lot arrives with a factory name and a score attached. See Green coffee buying and Coffee scoring.

What AA is often assumed to include, and does not

AssumptionReality
A varietyAA lots routinely mix SL28, SL34, Ruiru 11 and Batian harvested together
A cup scoreAA carries no score; scoring happens separately, if at all
A processing methodNearly all Kenyan AA is [[Washed process
A specialty guaranteeSpecialty coffee is a defect count plus an 80-point cup — neither is a size
A regionAA is milled out of coffee from every growing zone in the country

The variety point is the one that frustrates buyers most. Kenyan smallholders deliver cherry to a cooperative “factory” — the local word for a wet mill — where several varieties are pulped, fermented and dried as one stream, then sized. By the time the letters are assigned, the plant is unrecoverable from the paperwork. This wiki’s SL28, SL34, Ruiru 11 and Batian notes all hit the same wall: variety-level Kenyan auction records essentially do not exist.

The flavour question

There is a house style attached to the name. Descriptions of Kenya AA converge on bright, lively acidity, wine-like fruitiness and sweet, floral aromas, with blackcurrant and passion fruit the two descriptors that appear most often, and a light but flavourful body.23

Read that as a description of good Kenyan washed coffee, not of the grade. The acidity comes from SL28-family genetics, high-altitude ripening and Kenya’s meticulous double-washing — none of which is what AA measures. An AA lot from an indifferent factory tastes like an indifferent coffee that happens to have large beans.

To verify — the altitude figures, and a conflict with this wiki's Kenya note

Trade pages tie AA to specific elevations: “higher than 6,600 feet above sea level” (≈2,010 m) in one,2 and “normally more than 2,000 metres” in the research behind this note. That sits above the range this wiki’s Kenya note records for the country as a whole — roughly 1,400–2,100 m, with 1,400–2,000 m given as the ideal band by a 2024 origin report.6 The two cannot both be typical. The likeliest reading is that the AA figures describe the top of the range rather than a requirement, and no altitude criterion appears in any grading rule consulted. Nothing here should be read as “AA means grown above 2,000 m.”

To verify — a second, unofficial layer of flavour grades

The research pass behind this note reports that some Kenyan exporters attach cup-based sub-grades to AA and AB — “TOP”, “PLUS (+)” and “FAQ” (fair average quality) — to differentiate lots beyond size, and that this system is not officially recognised by the Kenyan government. The claim comes from a single commercial SEO page (en.gafei.com) that was not read directly here, and no exporter offer sheet or Coffee Directorate document confirming it was located. Separately, Espresso & Coffee Guide describes a “Class” system numbered 1–10 that ranks quality within each grade.2 Whether TOP/PLUS/FAQ and Classes 1–10 are the same scheme, two schemes, or one scheme misdescribed is not established. Both are recorded as claims.

To verify — grade shares, and the prices attached to AA

Two commercial figures came through the research pass and neither is confirmed against an auction sheet:

  • AB is “around 40% of Kenya’s crop” and peaberries “around 5%.” Single source, a Kenyan producer’s knowledge page.3 Plausible and roughly matches the trade’s description of AB as the bulk grade, but no Coffee Directorate or Nairobi Coffee Exchange breakdown by grade was located.
  • Top AA lots “fetching USD 300–500+ per 50 kg bag,” with a cited high of $501 for Gachuiro Factory in Nyeri. This appears in a roaster’s marketing article (creativedrinkers.com) that was not read directly here. No sale date, buyer or hammer price from a primary NCE catalogue backs it. The Nairobi Coffee Exchange note’s standing rule applies: do not state an NCE record price. The same article’s claim that a particular retail lot scored 87 points is a roaster’s internal cupping result, not an SCA, CQI or ACE score, and is not recorded as a fact here.

Why the whole thing persists

A size-based catalogue survived ninety years because it is cheap, fast and impossible to argue with. Screens do not have opinions. A national auction that has to price thousands of lots a week from tens of thousands of smallholders cannot cup them all to a consistent standard, and a mechanical sort is the only classification that scales to that.

The cost is that Kenya, which built one of the most transparent price-discovery systems in coffee, catalogues its crop by the one attribute a drinker cannot taste. That is the trade-off recorded on the Nairobi Coffee Exchange note in full, and “Kenya AA” is its two-letter summary.

Footnotes

  1. Trabocca — Kenya Grades Explained — green coffee importer; confirmed via WebFetch; source of the AA screen 17/18 definition, the AB 16/17 figure, the 5% tolerance on AA/AB/PB, the attribution of the standards to the Department of Agriculture, Coffee Directorate and NCE, and the warning that size does not guarantee flavour ↩ ↩2 ↩3 ↩4 ↩5 ↩6 ↩7 ↩8 ↩9

  2. Espresso & Coffee Guide — Kenya Coffee Grading — confirmed via WebFetch; source of the screen 17/18 figure, the eight-grade list, the 6,600 ft altitude claim, the floral/passion fruit/wine descriptors and the Class 1–10 system ↩ ↩2 ↩3 ↩4 ↩5 ↩6 ↩7 ↩8

  3. Solai Coffee — Kenyan Coffee Grades — Kenyan coffee producer’s knowledge page; confirmed via WebFetch; source of the 7.2 mm figure for AA, the alternative screen numbers for the minor grades, the “policy by law and a Kenya Auction requirement” phrasing, the AA flavour description and the AB 40% / PB 5% crop shares ↩ ↩2 ↩3 ↩4 ↩5 ↩6

  4. Perfect Daily Grind — Kenya AA, Colombia Supremo: Understanding Coffee Grading — trade publication; confirmed via WebFetch; source of the AA/Supremo equivalence, the “larger beans are better beans… not accurate” statement, and the size-then-density-then-cupping sequence ↩ ↩2 ↩3 ↩4

  5. Nairobi Coffee Exchange — official site — names “AA, AB, PB, and more” among the grades traded ↩

  6. Genuine Origin — Kenyan Coffee Origin Report 2024 — source of the eight-grade list and the 1,400–2,000 m ideal-altitude band used for the comparison above ↩ ↩2

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