Kenyan Coffee Bean Grades: Size, Screen Size and Altitude Classifications

When you buy Kenyan specialty coffee, have you ever wondered what makes one bean more expensive—or flavorful—than another? It’s not just about origin. Kenyan coffee beans are sorted, screened, and graded based on measurable physical traits and growing elevation, all of which directly impact cup quality. These classifications help roasters select beans with predictable profiles, and help buyers understand what they’re paying for.

Kenyan coffee beans are graded primarily by two systems: screen size (via numbered sieves) and altitude. Screen sizes range from 8 to 20+, with higher numbers indicating larger beans. Altitude grades, meanwhile, use letters like S.H.B. (for beans grown 4,500 meters and above) down to G.W. (for beans grown below 2,000 meters). Together, these metrics indicate bean density, potential cup complexity, and market value.

What Are Flat and Peaberry Coffee Beans?

Coffee cherries usually contain two seeds that develop flat sides facing each other—these are called flat beans (or “” in Chinese). But about 5% of cherries produce a single, round seed known as a peaberry (or “”). Though peaberries look different, they don’t inherently taste better. Both flat and peaberry beans can produce excellent coffee, and both are graded using the same systems.

How Kenyan Coffee Beans Are Sized: Screen Size and Sieve Numbers

Kenyans—and many other producing countries like Brazil, Colombia, and Tanzania—use sieve or screen sizes to classify beans by diameter. This is done with metal screens featuring holes of specific diameters. Beans are shaken through these screens, and those that pass through a certain mesh are grouped accordingly. This doesn’t guarantee quality, but it does ensure uniformity in roasting and brewing behavior.

The most desirable Kenyan coffees often fall into the 17–18 screen sizes—indicating large, dense beans with potential for greater sweetness and clarity. Peaberries, if sorted at higher mesh numbers like 11–13, are also considered premium due to their concentrated flavors.

How Altitude Determines Kenyan Coffee Grades

Altitude plays a critical role in bean density, acidity, and sweetness. Kenyan coffee is graded not just by size, but also by the elevation at which it’s grown. Higher-altitude farms (above 1,500m) tend to produce slower-maturing cherries with more complex acids and intense aromatics. These elevations are categorized into seven official grades, defined by specific altitude bands:

Coffees grown at the highest altitudes (S.H.B., above 4,500m) are denser, brighter, and more sought-after. These beans command premium prices due to their concentrated sugars and acids, which translate into vibrant, complex cups. Lower altitude beans (G.W.) are more common and affordable, though still capable of good flavor depending on variety and processing.

The Role of Coffee Variety and Processing in Kenyan Flavor

Though not part of the official grading system, Kenya’s famed SL28 and SL34 varieties—developed by the Scott Labs in the 1930s—are central to the country’s coffee identity. These cultivars thrive at high altitudes and are known for their exceptional acidity, particularly citrus and blackcurrant notes. SL28 offers deep, wine-like fruitiness with strong umami undertones, while SL34 brings balanced fruit acid, nuttiness, and spice.

Kenyan processing also enhances these traits. Most Kenyan coffees are washed using a double fermentation method: after pulping, the beans ferment for 48 hours, then are washed to remove mucilage, followed by another 24-hour soak in clean water. This meticulous process brightens acidity and emphasizes fruit tones, complementing the effects of altitude and variety.

Frequently Asked Questions

What is the difference between flat beans and peaberry beans in coffee?

Flat beans are the usual coffee seeds, paired inside a cherry with flat sides touching. Peaberry beans are rare—about 5% of cherries produce a single, rounded seed instead of two flat ones. They are not inherently better tasting, but are often sorted and sold separately, sometimes at a premium. Both types are graded by the same size and altitude systems in Kenya.

How are Kenyan coffee beans sized?

Kenyan coffee beans are sized using numbered screens or sieves. Flat beans range from screen 20 (very large) down to 12 (very small). Peaberry beans are classified from screen 13–12 (large) down to 8 (small). Higher screen numbers mean larger, usually denser beans, which often roast more evenly and have more complex cup profiles.

What do the Kenyan coffee grade letters mean?

Kenyan coffee grades are indicated by letters such as S.H.B., H.B., and G.W. These correspond to the altitude the coffee was grown at. S.H.B. (Strictly High Grown) means the beans were grown at 4,500 meters or above, making them very dense and flavorful. Lower grades like G.W. are grown below 2,000 meters and are more common and less expensive.

Does altitude really affect coffee flavor?

Yes. Higher-altitude coffee cherries ripen more slowly due to cooler temperatures, allowing more complex sugars and acids to develop. Kenyan coffees grown above 4,000 meters, classified as S.H.B. or H.B., typically have brighter acidity, deeper sweetness, and more pronounced fruit flavors compared to lower-grown beans.

Why are SL28 and SL34 important in Kenyan coffee?

SL28 and SL34 are coffee varieties developed by Kenya’s Scott Laboratories in the 1930s. They are renowned for their outstanding cup quality, especially in high altitudes. SL28 offers intense citrus and blackcurrant with winey depth, while SL34 provides balanced fruit acids, nuts, and spices. These varieties are a big reason why Kenyan coffees are so distinctive.

Recommended FrontStreet Beans for Exploring Kenyan Coffee Profiles

FrontStreet Coffee’s Kenya Little Tomato highlights the classic Kenyan profile with its blend of SL28 and SL34 beans. It’s washed twice and roasted to a medium-light level, offering vibrant notes of cherry, pear, black plum, persimmon, and brown sugar. The cup is juicy, structured, and sweet with lingering caramel-like finish. Ideal for pour-over or cold brew. Freshly roasted within 5 days · Orders placed before 17:00 ship the same day · Next-day delivery across most of Guangdong Province.