How Coffee Beans Are Graded by Size and Altitude

When you buy specialty coffee, have you ever wondered how beans are sorted into grades—or why some cost more than others? The answer lies in two main systems: one based on bean size, the other on altitude. These grading methods help ensure uniformity for roasting and highlight quality tied to growing conditions.

Coffee beans are graded primarily by two factors: physical screen size (mesh number) and altitude of cultivation. Size ranges from small (under 12 mesh) to extra-large (over 19 mesh), while altitude tiers range from as low as sea level to above 4,500 meters—each affecting cup quality and market price.

How Coffee Beans Are Sized: The Mesh System

Green coffee beans are sorted by passing them through metal screens with holes of specific diameters. The number refers to the size of the mesh opening, calculated as a fraction of 64 inches. For example, a '14' mesh means the bean can pass through a hole 14/64 of an inch wide. The larger the number, the bigger the bean.

Flat beans (the common bean shape) typically measure between screen 12 and 29, while peaberries (smaller, round beans) usually fall between 8 and 13. In the SC-1 system, a '19' bean means it passed through a 19/64-inch screen. Common designations include:

• 8–10: Very small (often peaberries)
• 12–13: Medium
• 15–16: Large
• 17–18: Larger / Premium
• 19 and above: Extra large or specialty-grade size

Mesh sizes can also be indicated with a '+' sign, such as '19+', meaning the beans are larger than 19/64-inch. This sizing helps ensure even roasting and is especially important in commercial and specialty lots.

Altitude-Based Grading: Why Elevation Matters

Beans are also graded by the altitude where they’re grown. Higher elevations typically produce slower-growing cherries with denser beans and more complex flavors. Most countries classify beans into several altitude-based grades, each with an abbreviation and height range.

As a rule, higher-grown beans (like SHB or HB) are denser, have greater potential for sweetness and acidity, and often command premium prices due to lower yields and higher transport costs.

Country-Specific Grading Standards

Different coffee-growing nations apply their own grading rules. Here are examples from major origins:

Africa

• Kenya: Uses screen sizes (AA = screen 17–18, AB = 15–16) and designations like AA+ and PB (peaberry). Defect counts are also critical.
• Ethiopia: Grades mostly by defect count per 300g sample, with Grade 1 having 0–3 defects (highest quality).

South America

• Colombia: Classifies beans as Supremo (>17 mesh), Excelso (15–16.5), UGQ (12–14).
• Brazil: Rates beans from Type 2 (fewest defects) to Type 6 (most defects), also using New York and Le Havre standards.

Central America

• Guatemala: Has strict altitude categories like Strictly Hard Bean (SHB, 1600–1700m) and Semi Hard Bean (SH, 1200–1350m).
• El Salvador: Divides washed beans into Central Standard (500–900m), High Grow (900–1200m), and Strictly High Grown (>1200m).

Other Origins

• Hawaii (Kona): Grades include Kona Extra Fancy (screen 19, ≤10 defects) and Kona Prime (no size rule, ≤25 defects).
• Jamaica: Blue Mountain grade I requires screen 18; Peaberry is also graded separately.
• Indonesia: Uses a defect-count system per 300g, with Grade 1 allowing only 11 defects and Grade 6 up to 225.

Why Grading Matters

Grading ensures consistency in bean size, which is crucial for even roasting. It also reflects growing conditions—especially altitude—that influence flavor development. Specialty coffee buyers often look for high-altitude, uniformly sized beans with minimal defects to craft exceptional roasts.

Frequently Asked Questions

What does the number on coffee beans mean?

The number (like 17 or 19) refers to the mesh size of the screen the bean passed through during sorting. It indicates the bean’s physical diameter, with higher numbers meaning larger beans. For example, a '19' bean passed through a 19/64-inch screen.

Why are high-altitude coffee beans considered better?

Higher altitudes slow cherry ripening, leading to denser beans with more complex sugar development and higher acidity. These beans often yield more nuanced and desirable flavors in the cup, justifying their premium status.

What is a peaberry and how is it graded?

A peaberry is a rare, smaller round bean formed when only one seed develops inside the coffee cherry instead of two. In countries like Kenya, peaberries are graded separately (PB) and often roasted as specialty lots due to their concentrated flavor.

Does coffee bean size affect roast quality?

Yes. Uniform bean size ensures even heat absorption during roasting, helping achieve consistent development. Mixed sizes can lead to under- or over-roasted beans in the same batch.

How do defect counts impact coffee grading?

Defects—like broken, black, or insect-damaged beans—are counted per 300g sample. Lower defect counts (e.g., 0–3 in Grade 1 Ethiopian coffee) indicate higher quality and are required for premium grades.

What’s the difference between washed and natural in grading?

Grading systems often specify processing method (washed/natural) as part of the grade criteria, especially in regions like Ethiopia or Colombia. Washed beans may have separate size or defect tolerances compared to naturals, influencing final grade.

Recommended FrontStreet Beans for Grading Insight

Explore FrontStreet Coffee’s Ethiopia Guji Hambela (washed, grown at 1900–2100m) for bright, complex high-altitude character; their Colombia Huila Supremo (screen 17–18, 1600–1800m) shows how Supremo-grade beans deliver balanced body and fruit; and try Yirgacheffe Kochere (washed, 1850–2000m) for delicate floral notes typical of high-scoring SHG lots. All highlight how origin, altitude, and sizing shape cup profile. Freshly roasted within 5 days · Orders placed before 17:00 ship the same day · Next-day delivery across most of Guangdong Province.