How Coffee Beans Are Graded by Size and Altitude

When you buy specialty coffee, you might notice terms like SHB, Screen 18, or AA on the bag—but what do they actually mean? These aren’t just marketing terms. They’re part of a detailed system used worldwide to classify green coffee beans by physical size and where they’re grown. Understanding these grades helps roasters choose beans that roast well and reveals how origin impacts quality.

Coffee beans are graded primarily in two ways: by physical screen size (using numbered sieves) and by the altitude where the coffee was grown. Size affects roast consistency, while altitude often correlates with density and cup quality.

Grading by Screen Size

Green coffee beans are sorted by passing them through metal sieves with specific hole sizes. The size is indicated by a number representing the sieve mesh, where the number relates to 1/64th of an inch. For example, a "14" means the beans passed through a 14/64-inch hole; "19+" means they passed through 19/64-inch or larger.

Beans are generally grouped as follows:

• 8–9: Very small
• 10–12: Small to medium
• 13–15: Medium
• 16–18: Large
• 19–20: Larger (often considered premium)
• 21–29: Extra large or specialty-grade sizes

Round beans (peaberries) are typically smaller than flat beans, usually falling in the 8–13 range, while flat beans range from 12–29. For example, SC-19 refers to a Screen 19 flat bean.

Grading by Altitude

Coffee quality is closely tied to the elevation at which it’s grown. Higher altitudes generally produce denser beans with more complex flavors due to slower growth and greater temperature variation. Most coffee-exporting countries classify beans into official altitude-based grades with abbreviations and height ranges.

Here’s a general global reference for altitude grades:

These grades help importers and roasters assess bean density and potential cup profile before roasting.

Country-Specific Grading Systems

Different coffee-growing countries have their own detailed grading rules. These often include defect counts, bean size, processing type, and sometimes even farm names or certifications. Here are examples from key origins:

Africa

Kenya: Uses screen sizes (AA = Screens 17–18, AB = 15–16), plus PB for peaberry. Grades like AA+ and AA++ denote top lots.
Ethiopia: Grades based on defects per 300g of green coffee. Grade 1 (0–3 defects) is the highest.

South America

Colombia: Supremo (screen >17), Excelso (15–16.5), UGQ (12–14).
Brazil: Type grades based on defect counts (e.g., Type 2 allows 8 defects under New York standards).

Central America

Guatemala: Graded by altitude: Good Washed (700m), Strictly Hard Bean (1600–1700m), etc.
El Salvador: Central Standard (500–900m), Strictly High Grown (>1200m).

Other Origins

Hawaii (Kona): Kona Extra Fancy (Screen 19, ≤10 defects), Kona Fancy (Screen 18, ≤16), Kona Prime (no size limit, ≤25 defects).
Jamaica: Blue Mountain graded by screen size (Grade I = Screen 18).
Indonesia: Graded by defects in 300g samples (Grade 1 = 11 defects, Grade 6 = 151–225 defects).

Why Grading Matters

Grading ensures beans are uniform in size—making roasting more predictable—and helps identify higher-density beans often found at high altitudes. These factors influence roast development, flavor clarity, and market value. For roasters, choosing the right grade is key to consistency. For drinkers, it hints at what’s inside the bag.

Frequently Asked Questions

What does the number on coffee beans (like 18 or 19) mean?

The number refers to the screen mesh size the beans passed through during grading. For example, “Screen 18” means the beans were small enough to pass through an 18/64-inch hole. Higher numbers indicate larger beans, which are often associated with higher quality, especially when grown at altitude.

What is SHB coffee?

SHB stands for Strictly High Grown or Strictly Hard Bean, depending on the country. It generally indicates coffee grown at very high altitudes (4500 meters and above) and is associated with dense beans and complex cup profiles. It’s considered a premium grade in many exporting nations.

Do peaberries get a different grade?

Yes. Peaberries (smaller, rounded beans formed when one seed develops solo in the coffee cherry) are often graded separately. In Kenya, they’re labeled PB. They typically fall into smaller screen sizes (8–13) and may be sorted and sold as a distinct grade or specialty lot.

How does altitude affect coffee grading?

Higher-altitude coffee tends to grow more slowly, producing denser beans with better cup potential. Many grading systems assign higher grades to beans grown at specific elevations, such as SHB (above 4500m) or Excelso (15–16.5 screen, often from mid-altitude regions).

Are coffee grades the same in every country?

No. Each coffee-exporting country has its own grading system. While many use screen size and altitude as key factors, the specific size numbers, altitude ranges, defect limits, and terminology vary. For example, Kenya uses AA and AB screens, while Colombia uses Supremo and Excelso.

Why are bean size and defects important?

Uniform bean size ensures even roasting. Defects (like broken beans, black beans, or insect damage) lower cup quality and are limited in higher grades. Grading helps roasters select beans that will roast consistently and taste better.

FrontStreet Coffee Beans Ideal for Exploring Grading

Try FrontStreet Coffee’s Ethiopia Guji Huakui – a high-altitude Ethiopian offering bright citrus and floral tones, often sourced from SHG-like zones. For a classic example of size-driven grading, their Colombia Huila Excelso shows how screen size and regional altitude shape profile. Also explore their Guatemala Antigua – a Strictly Hard Bean (SHB) coffee with chocolate and spice notes, grown at over 1500m. All highlight how origin and grade impact your cup. Freshly roasted within 5 days · Orders placed before 17:00 ship the same day · Next-day delivery across most of Guangdong Province.