Tanzania Coffee Grading:
AA, AB & Peaberry

Tanzania Coffee Grading: An Overview

Tanzania uses a screen-size-based grading system to classify green coffee by bean size — a system inherited from British colonial administration and still used across East Africa today. The grades (AA, A, AB, B, PB, C, and others) tell you the physical size of the bean, not its cup quality — though size and quality are correlated in practice because larger beans tend to come from higher-altitude, more slowly developed cherries.

Understanding what each grade means — and what it doesn't tell you — is essential for making informed sourcing decisions. A lot labelled "Tanzania AA" covers an enormous range of potential quality. AA combined with a specific origin, processing method, varietal, SCA score, and altitude data is a meaningfully different product from "Tanzania AA" on its own.

AA Grade: The Largest Beans

AA is the highest size grade in the Tanzania grading system, consisting of beans that pass through a screen size 18 (7.2mm aperture) — the largest screen used in Tanzanian grading. AA beans are the biggest, densest beans from a given lot, and they typically come from the highest-altitude farms where slow cherry development produces the largest seeds.

Because larger beans roast more evenly and tend to produce more complex cups, AA is the grade most associated with specialty-quality Tanzania coffee. It is the grade primarily traded in specialty markets and the one you'll most commonly see offered by specialty importers and direct-trade sources like Kilimanjaro Beans.

Key caveat: AA grade tells you size, not quality. A well-grown, carefully processed AA lot from a 1,800m cooperative washing station on Kilimanjaro is a fundamentally different product from an AA lot from a 900m lowland estate, even though both carry the same grade designation. SCA score, altitude, origin, and processing method are the quality indicators — AA is a size indicator.

A Grade

Grade A consists of beans that pass screen 17 (6.8mm) but not screen 18 — slightly smaller than AA. In practice, A grade lots from high-altitude origins can be excellent — the size difference between AA and A from the same washing station is minimal and the cup quality difference is often negligible in blind cupping.

A grade is less commonly seen in specialty markets than AA, as most specialty-focused washing stations screen their best lots for AA export. When encountered from a reliable high-altitude source, A grade can represent outstanding value.

AB Grade

AB grade combines beans from screens 15 and 16 (6.0–6.4mm aperture) — beans that are smaller than A grade but not small enough to be considered B or C. The "AB" designation is a common one in East African grading: rather than separate A and B grades into individual lots, many washing stations combine them for export efficiency.

AB lots from high-altitude origins can still be specialty grade — altitude and processing quality matter more than bean size for cup quality in most cases. However, the size difference does correlate with slightly less dense beans, which can produce slightly less even roasting. AB is commonly used in blends or as a more price-accessible single origin offering.

B Grade

B grade (screen 14 and below) consists of smaller beans, typically from lower-altitude farms or processing that produces smaller seed development. B grade is rarely seen in specialty markets and is primarily traded in commercial coffee channels. Cup quality is typically lower than AA or A from the same origin.

Peaberry (PB) Grade: The Most Distinctive

Peaberry is not a size grade in the conventional sense — it is a natural mutation that occurs in approximately 5% of coffee cherries. Normally, each coffee cherry contains two seeds that develop facing each other, producing the characteristic flat-faced bean of conventional coffee. In a peaberry cherry, only one of the two seeds is fertilised, and it develops alone inside the cherry — growing into a small, rounded, oval-shaped bean with no flat face.

Because the peaberry bean developed alone, it absorbed all the nutrition that would normally have been shared between two seeds. Many specialty tasters find peaberry lots more concentrated in flavour — brighter acidity, more intense sweetness, and greater aromatic complexity. The rounded shape also promotes more even drum movement during roasting, which some roasters find produces more even development.

Tanzania Kilimanjaro Peaberry is among the most sought-after specialty lots from the region. Our Lot 005 Songwe Peaberry scores 85.75 SCA — a score that reflects the concentrated quality typical of good peaberry lots.

C Grade and Mbuni

C grade consists of the smallest beans and is primarily a commercial-grade product. Mbuni refers to natural-processed (dry-processed) coffee in Tanzanian classification — not a size grade but a processing distinction. Mbuni can range from commercial to specialty quality depending on cherry selection and processing conditions.

The Full Tanzania Grade Hierarchy

What Grade Should Roasters Source?

For specialty single origin filter coffee, AA is the standard starting point — it offers the best combination of bean density, roast evenness, and cup potential. Peaberry is worth sourcing as a distinct product when you can find a high-scoring lot — it makes an excellent separate offering with its own provenance story.

Do not use grade alone to evaluate a Tanzania lot. Always request the full specification: grade, origin (region and washing station), altitude, varietal, processing method, harvest date, and SCA score with full breakdown. A Tanzania AA at 84 SCA from a named Kilimanjaro cooperative at 1,800m is a fundamentally different purchase from a Tanzania AA at 80 SCA from an unnamed estate at 1,000m.