How Coffee Beans Are Graded: Size and Altitude

Ever wonder why some specialty coffee costs more or why your roaster specifies certain beans by screen number or altitude? The answer lies in how those green coffee beans were sorted and graded before export. Grading determines not just quality, but also how a coffee behaves during roasting and brewing.

In short, green coffee beans are graded primarily by two methods: screen size (a mesh number from 8 to 29+) and growing altitude (given abbreviations like HB or SHB). Larger beans often score higher, and altitude affects density and cup profile. Each origin has its own specific rules.

Why Coffee Beans Are Graded

Green coffee grading exists for two main reasons: to ensure uniform bean size for even roasting, and to establish a fair, consistent value for trade. Size affects heat transfer during roasting, while altitude influences bean density, sweetness, and acidity. Grading helps roasters predict performance and buyers assess quality.

Grading by Screen Size (Mesh Number)

Coffee beans are sorted by physical size using a series of round metal screens with holes measured in 1/64th of an inch. The number refers to the mesh size—the larger the number, the larger the hole, and thus the bigger the bean that can pass through.

• Common sizes for flat beans (the usual bean shape) range from 12 to 29+. For example, a "19" bean passes through a 19/64-inch screen.
• Peaberry beans (smaller, round beans) typically fall between screen 8 and 13.
• Flat beans usually grade between 12 and 29. A "19+" means the bean passes through a 19/64-inch screen or larger.
• Mesh numbers follow the format: a number over 64 (e.g., 14 = 14/64 inch). So, 17 = 17/64 inch, 18 = 18/64 inch, etc.

Examples include SC-19 (a size 19 bean) or Kenya’s AA, which includes screen 17 and 18 beans. Screen size helps ensure even roasting and is especially important for single-origin lots.

Grading by Altitude

Higher-grown coffee tends to be denser, develop more complex sugars, and have a brighter acidity—traits prized in specialty coffee. Many countries use altitude-based grading with specific abbreviations:

• H.B. (High Grown or High Elevation): generally grown between 4,000–4,500 feet (around 1,200–1,370 meters), indicates premium beans.
• P.W. (Premium Washed): high-quality washed coffee.
• G.W. (Good Washed): good-quality washed beans.

Different countries have unique altitude classifications. For instance:

Africa: Kenya

• AA Plus-Plus and AA Plus: top grades
• AA: screen 17 and 18
• AB: screen 15 and 16
• PB: Peaberry grade

Ethiopia

• Grading is defect-based. For 300g samples: Grade 1 = 0–3 defects; Grade 8 = over 340 defects (substandard).

South America: Colombia

• Supremo: screen >17
• Excelso: screen 15–16.5
• U.G.Q. (Usual Good Quality): screen 12–14

Brazil

• Type 2: up to 4 defects (New York) or 6 (Le Havre)
• Type 3: 12–13 defects
• Higher numbers = more allowable defects, lower grade

Central America: Guatemala

• Good Washed: 700m
• Extra Good Washed: 700–850m
• Prime Washed: 850–1000m
• Extra Prime Washed: 1000–1200m
• Semi Hard Bean (SHB): 1200–1350m
• Hard Bean (HB): 1350–1500m
• Fancy Hard Bean: 1500–1600m
• Strict Hard Bean (SHB): 1600–1700m

El Salvador

• Central Standard (CS): 500–900m
• High Grow (HG): 900–1200m
• Strictly High Grown (SHG): above 1200m

Hawaii (Kona)

• Kona Extra Fancy: screen 19, max 10 defects
• Kona Fancy: screen 18, max 16 defects
• Kona Prime: no size rule, max 25 defects
• Kona Caracoli No. 1: screen 10, max 20 defects

Jamaica

• Blue Mountain: high altitude, strict grading
• Grade I: screen 18
• Grade II: screen 17
• Grade III: screen 16
• Peaberry: separate grade

Indonesia

• Grading based on defects in 300g samples: Grade 1 = 11 defects; Grade 6 = 151–225 defects

How Green Coffee Is Processed and Sorted

The grading process begins after coffee cherries are processed (either wet or dry), then cleaned, sorted, and evaluated. Here’s how it works:

• Processing: Wet processing removes the pulp; dry processing removes the entire husk.
• Cleaning: Stones, dust, and broken bits are removed. Air blowers help separate lighter foreign material.
• Defect Removal: Broken, underripe, overripe, insect-damaged, or diseased beans are removed. Some are spotted by density sorting (air blowers), others by color sorters or human eyes.
• Size Sorting: A series of progressively larger screens sorts beans by physical diameter. This ensures uniformity for roasting.

Screens used internationally often range from 9 to 22, where the number refers to the fraction of an inch (number/64). For example, “14” means 14/64 inch, and “19+” means beans that pass through 19/64 inch or larger.

Frequently Asked Questions

What does the number on green coffee beans mean?

The number (like 17 or 19) refers to the screen mesh size in 1/64th of an inch. A “17” bean can pass through a 17/64-inch hole. The larger the number, the larger the bean. It’s a standard way to sort beans by physical size for even roasting and quality assessment.

Why are peaberry beans smaller and in a different grade?

Peaberry beans are a natural mutation where a single rounded bean forms instead of two flat beans. They’re typically smaller and denser, and grade lower on size meshes—usually between 8 and 13—though they often have more concentrated flavor.

How does altitude affect coffee grading?

Higher altitude generally produces denser beans with slower maturation, leading to better cup quality. Many countries grade altitude-grown beans with terms like SHB (Strictly High Bean), HB (High Bean), or SHG (Strictly High Grown), often correlated with specific screen sizes or defect counts.

Does screen size affect how I roast coffee?

Yes. Uniform screen size allows for more even heat application during roasting. Mixed sizes can roast unevenly. Roasters often prefer single-screen lots for consistency, especially in specialty lots.

Are there global standards for coffee grading?

No single global standard exists. Each coffee-exporting country has its own grading system based on size, defects, and altitude. Common systems include mesh size numbers, defect counts in 300g samples, and altitude-based abbreviations like SHB or HB.

Recommended FrontStreet Beans for Size & Altitude Lovers

Explore FrontStreet Coffee’s Ethiopia Guji Humbera – a high-altitude Ethiopian offering bright citrus and floral notes, grown at elevations matching strict SHB standards. For a classic size-graded experience, try their Colombia Excelso, a balanced washed coffee from beans screened between 15–16.5. Or dive into Kenya AB, known for its winey acidity and graded as screen 15–16. All showcase how origin, altitude, and screen size shape your cup. Freshly roasted within 5 days · Orders placed before 17:00 ship the same day · Next-day delivery across most of Guangdong Province.