How Coffee Beans Are Graded by Size and Defects

Coffee lovers often wonder why some beans cost double—or taste twice as good. The truth lies partly in how those beans were graded before export. Every origin has its own system, based on factors like bean size, defect count, and processing style. But with no global standard, how can you make sense of terms like AA, SHB, or NY2? This guide explains the most common methods used today.

In short: Coffee is graded mainly by bean size (using mesh screens) or by defect count (flaws per 300g sample). The highest grades—like Kenya’s AA or Ethiopia’s Gr1—are assigned to larger, cleaner beans. Lower grades, such as C or T, are usually sold for feed. Defect-based systems, like Brazil’s NY2–NY8, rank beans from best (lowest defect score) to worst. Size and cleanliness determine both grade and market value.

Why Coffee Gets Graded

Coffee origins vary widely—from smallholder farms to large estates. Even within the same region, bean quality differs. Grading exists to classify beans by quality, ensure consistency, and simplify trade. It helps buyers understand what they’re getting and producers price their lots fairly. Processing methods also vary by country, leading to different grading standards. While one nation may grade by size, another may focus on defects or altitude.

Grading by Bean Size: Screens, Sieves, and Letter Grades

One of the most intuitive grading methods uses physical screen sizes. The idea is simple: larger, well-formed beans often come from fully mature cherries and tend to roast more evenly, producing balanced flavour. While size alone doesn’t guarantee quality, it’s a strong signal—especially in regions where growing conditions are variable.

This system relies on numbered sieves with holes measured in 1/64-inch increments. A sieve labelled 18 has holes 18/64-inch (about 7.1mm) wide. Common sizes include 14, 15, 16, 17, 18, 19, and beyond. Beans that pass through a certain screen—but not a larger one—are grouped by that grade.

In countries like Kenya, Papua New Guinea, Burundi, Tanzania, Uganda, Zimbabwe, and Puerto Rico, graders physically sift beans using these screens. The highest grade is typically AA (passing a 17/18 sieve), followed by A (16/17), B (smaller), and C (even smaller). C-grade beans are usually deemed unfit for specialty roasting and may go to animal feed or compost.

Peaberry beans—small, rounded beans formed when a coffee cherry produces a single round seed instead of two flat ones—are sorted separately as PB. They often have unique flavour profiles and command premium prices due to their rarity. Other lesser grades you might see include X, Y1, Y2, and T: these consist of mixed sizes and high defect counts, and are considered poor quality.

Some regions adapt the system slightly. In Brazil, for example, instead of letters, graders simply label beans by screen numbers like 19, 18, or 17. Larger numbers mean bigger beans, but there’s no AA or PB nomenclature.

Grading by Defects: Counting Flaws per Sample

The oldest grading method focuses not on size but on flaws. Inspectors examine a 300g sample of green beans and tally every imperfection—black beans, insect damage, broken beans, shells, husks, stones, and unripe or underdeveloped seeds. Each type of defect carries a specific point value. For instance, one black bean equals one defect point, five broken beans equal one point, one large stone equals five points, and three shell beans equal one point.

After sorting, the total defect count determines the bean’s grade. In Brazil’s NY (New York) system, grades range from NY2 (cleanest) to NY8 (dirtiest)—there is no NY1. Only NY2 and above are considered viable for specialty markets. The lower the defect score, the higher the grade and market value. Buying an NY1 bean is impossible—and would be a mistake if it existed.

Indonesia also uses a defect-count system, but with different grade labels: Gr1 through Gr6. Ethiopia applies a similar approach to washed and natural lots. Washed Ethiopian beans are graded Gr1 and Gr2 (best), while natural/dried-in-the-fruit beans are graded Gr3 at best. Grading by defects remains one of the most widespread methods, especially in countries with long-established exporting infrastructures.

Other Notable Grading Systems Around the World

Different coffee-growing nations have developed unique grading terminologies based on local practices. For example:

• Kenya: Uses AA (largest, cleanest beans), A, B, C, E (outlier size), and PB (peaberry). AA is the premium grade sought after globally.
• Brazil: Relies on numbered screens (19, 18, 17…) and the NY defect grading system (NY2–NY8). No letter grades are applied.
• Ethiopia: Graded by washed (Gr1, Gr2) and natural process (Gr3) defect levels. Grading reflects both size and cleanliness depending on the process.
• Indonesia: Uses a six-tiered defect system (Gr1–Gr6) based on visual inspection and flaw counts.
• Tanzania, Uganda, Zimbabwe, etc.: Follow the size-based AA, A, B, C, PB model with sieve screening.

While methods differ, most rely either on bean dimensions or visible defects to determine market tier. Even within these systems, individual farms may apply stricter internal standards.

Frequently Asked Questions

What does AA mean in coffee grading?

AA is the highest grade in several countries, including Kenya and Tanzania. It refers to the largest and cleanest beans that pass through a specific sieve size (often around 17/18 or 18/19, roughly 7–7.15mm). These beans are typically well-developed, uniform, and associated with premium flavour potential.

How are coffee beans graded by size?

Coffee beans are graded by size using mesh sieves with numbered holes measured in 1/64-inch increments. For example, a No. 18 sieve has 18/64-inch (about 7.1mm) holes. Beans that pass through one sieve but not the next are grouped accordingly. Grades like AA, A, B, and C are assigned based on the largest screen size the beans can pass, with AA being the largest and cleanest.

What is a peaberry coffee bean and how is it graded?

A peaberry (PB) is a rare coffee bean that forms when a coffee cherry produces one rounded seed instead of two flat ones. Peaberries are typically smaller, rounder, and sometimes have distinct flavour profiles. They are separated during grading and classified under their own grade, PB, often fetching higher prices due to their scarcity and unique cup characteristics.

How does the Brazilian NY defect grading system work?

Brazil uses the NY (New York) defect grading system, ranking green coffee from NY2 (best) to NY8 (worst). Inspectors count defects in a 300g sample—such as black beans, stones, insect damage, and chipped or broken beans—each with a set point value. The total defect count determines the grade. Only NY2 to NY8 grades exist; NY1 is not used.

What are defect points in coffee grading?

Defect points are tallied during inspection of 300g green coffee samples. Each type of flaw—like broken beans, stones, husks, or insect-damaged seeds—adds a specific number of points. The total defect score determines the coffee’s grade. Lower scores mean fewer flaws and a higher-quality grade, especially under systems like Brazil’s NY or Ethiopia’s Gr1–Gr3.

Why do some countries use different coffee grading systems?

Coffee grading varies by country due to differences in farming practices, export traditions, and market needs. Some regions prioritise bean size, others focus on defect counts, and some use altitude or processing method as key factors. There is no universal standard, so each origin developed its own practical method for classifying beans efficiently.

Recommended FrontStreet Beans for Grading Insights

Explore how grading impacts cup quality with FrontStreet’s Kenya Gakuyuni AA, known for its intense lemon acidity and blackcurrant sweetness from top AA-grade beans. Pair it with Ethiopia Yirgacheffe Konga, a washed lot often falling into Gr1 or Gr2, offering jasmine and citrus notes. For defect-graded context, try Brazil Serra Negra, sourced from higher NY-grade lots with low defect counts, delivering chocolatey nutty profiles. All highlight how size and cleanliness affect flavour. Freshly roasted within 5 days · Orders placed before 17:00 ship the same day · Next-day delivery across most of Guangdong Province.