How Kenyan Coffee Is Graded by Size, Shape, and Weight

Ever wonder why some Kenyan coffees cost more than others, even though they all come from the same country? The difference often comes down to how the beans are graded—not by flavor alone, but by physical traits like size, shape, and density. These objective measures help separate the exceptional beans from the average ones before they even reach your cup.

Quick answer: Kenya’s top-grade coffee is AA (17–18 mesh), followed by AB (15–16 mesh), PB (peaberry, 15+ mesh), and E (elephant beans, 18+ mesh including peaberries). Lower grades include T, C, and HE, while ungraded beans fall under UG1 or UG2. Light or defective beans are labeled MBUNI.

What Determines Kenya Coffee Grades?

Kenya grows some of the most sought-after specialty coffee in the world, thanks in part to high elevations—often 1,500 to 2,000 metres above sea level—and ideal conditions of rainfall, sunlight, temperature, and volcanic soil. These factors slow down cherry development, leading to denser beans with more pronounced acidity and complexity. But not all beans from Kenya meet the highest standards. That’s where grading comes in.

Kenya’s Official Coffee Grade System

The Kenyan coffee grading system classifies green beans primarily by screen size (measured in mesh), shape, weight, and defect levels. The system is applied to washed, processed beans that have been carefully handpicked, sorted to remove underripe or overripe cherries, fermented for around 36 hours, sun-dried on raised beds, and milled to remove the parchment layer. The resulting green beans, known for their vibrant blue-green colour, are then graded as follows:

• E (Elephant Bean): 18 mesh and above, includes peaberries. These large beans are relatively rare.
• AA: 17–18 mesh. This is Kenya’s highest and most prized grade, known for larger beans and typically higher cup quality.
• AB: 15–16 mesh. A blend of the A and B grades, AB makes up a large portion of Kenya’s export volume and offers good balance.
• PB (Peaberry): 15 mesh and above. Peaberries occur when a coffee cherry produces a single round bean instead of two flat ones. They account for about 10% of Kenya’s crop and are often prized for concentrated flavours.
• T: Below 12 mesh. These beans are small, often broken, lightweight, and tend to have more defects.
• C: 12–14 mesh, along with lightweight beans from the PB grade filtered through air classification. Generally lower in cup quality.
• TT: Light beans removed from AA and AB grades via air separation. These are also lower density.
• HE (Hulled Ears): Any beans that don’t fit into the other defined grades.

Ungraded and Natural Processed Kenyan Coffees

Not all Kenyan coffee goes through the official graded system. Beans that haven’t been officially sorted by size and quality fall under the category UG (ungraded). These are further divided into:

• UG1: Includes E, AA, AB, and PB grades that somehow missed the official grade criteria.
• UG2: Comprises C, TT, T, and HE grades.

Additionally, there’s MBUNI—Kenyan natural (dry-processed) coffee. These beans are sorted using gravity tables and classified into:

• MH (Heavy Mbuni): Heavier beans, yellowish in colour, free from black beans, husks, or broken pieces. They have typical natural process flavours with no taste defects.
• ML (Light Mbuni): Yellow-green beans that may have a few insect-damaged or black beans, but no foul odours or broken fragments. Cup quality avoids earthy or off flavours.

Why Size and Density Matter in Coffee Grading

Larger, denser beans often mature more slowly at high altitudes, allowing for more complex sugars and acids to develop during cherry growth. That’s why grades like AA and PB are so valued—they’re more likely to come from slow-maturing, high-altitude beans with superior cup characteristics. While grading doesn’t guarantee flavour, it’s a strong indicator of bean quality and processing consistency.

Frequently Asked Questions

What is the highest grade of Kenyan coffee?

The highest grade is AA, which includes beans that are 17–18 mesh in size. These beans are typically larger, denser, and associated with higher cup quality, especially when grown at high altitudes.

What does PB mean in Kenyan coffee?

PB stands for peaberry, a rare coffee bean that forms when a single round bean develops inside the coffee cherry instead of the usual two flat beans. In Kenya, PB beans are usually 15 mesh and above, and make up around 10% of the crop.

What is the difference between AA and AB coffee grades?

AA beans are 17–18 mesh, considered the top grade in Kenya, while AB beans are slightly smaller at 15–16 mesh and are a mix of the former A and B grades. Both are washed processed, but AA beans are generally larger and more uniform.

What are T and TT grades in Kenyan coffee?

T grade includes beans under 12 mesh that are often small, broken, or defective. TT grade consists of light beans removed from the AA and AB grades via air classification, and also tends to be of lower density and quality.

What is MBUNI coffee?

MBUNI refers to Kenyan coffee processed using the natural (dry) method rather than washed. It is sorted by gravity into MH (heavier, defect-free beans with typical natural flavours) and ML (lighter beans that may have minor defects but no major off-flavours).

What does UG mean in Kenyan coffee grading?

UG stands for ungraded coffee. UG1 includes E, AA, AB, and PB beans that did not meet official grade standards, while UG2 covers C, TT, T, and HE grades.

Recommended FrontStreet Kenya Coffees for Tasting Grade Differences

Try FrontStreet’s Kenya Little Tomato, a single-origin Kenyan coffee showcasing the signature bright acidity and fruity complexity typical of high-grade beans like AA and AB. It highlights flavours of tomato, citrus, and dark berry, produced from the famed SL28 and SL34 varieties. For peaberry fans, FrontStreet’s Kenya PB offerings (when available) deliver concentrated sweetness and intensity in a small, dense bean. These beans highlight why grading matters—size, density, and processing all influence cup profile. Freshly roasted within 5 days · Orders placed before 17:00 ship the same day · Next-day delivery across most of Guangdong Province.