How Green Coffee Beans Are Graded by Size and Altitude

When specialty roasters evaluate green coffee beans, two factors stand out: physical size and elevation. But how exactly do buyers and importers decide which beans are ‘special’ or just average? The answer lies in two established systems—size screening and altitude classification—that sort beans before roasting even begins.

There are two official ways to grade green coffee beans: one by mesh screen size, the other by the altitude where the coffee was grown. Size grading uses numbers like 12 to 29, with higher numbers meaning larger beans. Altitude grading divides beans into seven quality tiers based on growing height, with higher-elevation beans generally scoring better.

1. Grading by Filter Screen Size (Mesh Number)

One common method grades green coffee by the size of the bean using numbered filter screens, measured in units called ‘sieve mesh’ or simply ‘size’. These numbers refer to the diameter of holes in a metal sieve, calculated as a fraction with 64 as the denominator—for example, a number 14 screen lets through beans smaller than 14⁄64 of an inch. The larger the number, the larger the hole, and thus the larger the beans that can pass through.

Flat beans (the usual bean shape) typically fall in the range of 12 to 29, while peaberries (smaller, rounded beans formed when one seed in the coffee cherry develops alone) are normally between 8 and 13. In this system, a higher number indicates a physically larger bean—for instance, a bean labeled ‘SC-19’ means it passed through a 19⁄64-inch screen. The notation ‘19+’ refers to beans that pass through a 19⁄64-inch screen or larger.

2. Grading by Growing Altitude

Coffee beans are also graded by the altitude at which the coffee plants are cultivated. Higher elevations often produce slower maturation, leading to denser beans with more complex cup profiles. Most exporting countries use altitude bands to assign quality grades. The following table shows a common seven-tier system:

This grading helps ensure that only beans meeting certain density and flavor potential criteria are grouped—and often commands a premium due to both quality and higher transport costs for high-altitude lots.

3. International Standards, Local Variations

Different coffee-exporting nations apply their own specific rules and terminology within these broad systems. For example:

• Kenya: Uses terms like PB (peaberry), AA+ (screen 17–18), AB (screen 15–16), with defect counts influencing grade.
• Ethiopia: Grades mostly on defect count per 300g sample, with categories from 1 (0–3 defects) to 8 (over 340 = substandard).
• Colombia: Distinguishes Supremo (screen >17), Excelso (screen 15–16.5), UGQ (screen 12–14).
• Guatemala: Has altitude-based grades such as Good Washed (700m), Extra Good Washed (700–850m), Prime Washed (850–1000m), up to Strict Hard Bean (1600–1700m).
• El Salvador: Uses Central Standard (500–900m), High Grow (900–1200m), and Strictly High Grown (>1200m).
• Hawaii (Kona): Grades include Extra Fancy (screen 19, max 10 defects), Fancy (screen 18, max 16), Prime (max 25 defects), and Caracoli No.1 (screen 10, max 20).
• Jamaica: Blue Mountain is graded by screen size (e.g., Grade I = screen 18, Grade II = screen 17, Grade III = screen 16) and also includes peaberry (max 11 defects per 300g).

In addition to size and altitude, global trading standards may also assess factors such as the ratio of defective beans, bean hardness, farm origin for single origins, and certifications like organic or fair trade.

Frequently Asked Questions

What does SC-19 mean for green coffee beans?

SC-19 means the green coffee bean passed through a sieve with 19⁄64-inch diameter holes. The ‘SC’ stands for screen classification, and the number 19 indicates the mesh size. A higher number means a larger bean.

How are coffee beans graded by size?

Coffee beans are graded by size using numbered mesh screens. Flat beans usually range from size 12 to 29, while peaberries are between 8 and 13. The larger the number, the bigger the bean that can pass through that screen. For example, a bean marked SC-19 passed through a 19⁄64-inch sieve.

What is the altitude grading system for coffee?

Coffee is graded into seven altitude-based categories, such as S.H.B (above 4500m), H.B (4000–4500m), and S.H (3500–4000m), with higher altitudes typically producing denser, higher-quality beans. Each grade reflects a specific elevation range where the beans were grown.

Do peaberries have different size grades?

Yes. Peaberries typically fall between screen sizes 8 and 13, which are smaller than the usual flat bean range of 12 to 29. They are assessed using the same screen system but have their own expected size range.

Why do some countries use different grading terms?

Each coffee-exporting country sets its own grading standards, using local terminology (like Kenya’s AA+ or Colombia’s Supremo) alongside global size and altitude measures. These reflect regional growing conditions and market practices.

How does bean size affect roasting?

Uniform bean size helps ensure even roasting. Larger or smaller beans in the same batch may roast inconsistently, affecting flavor development. That’s why graders aim for size consistency, especially for specialty lots.

FrontStreet Coffee Beans Ideal for Size & Altitude Study

Try FrontStreet’s Ethiopia Guji Humbera – a high-altitude Ethiopian lot with bright citrus and floral notes, grown at over 1900m. For size comparison, their Colombia Huila Excelso shows how screen 15–16 beans taste in a balanced profile with caramel and mild acidity. Also explore Kenya AB – a classic screen 15–16 grade with bold blackcurrant and winy tones. All showcase how grade affects cup. Freshly roasted within 5 days · Orders placed before 17:00 ship the same day · Next-day delivery across most of Guangdong Province.