How Coffee Beans Are Graded by Size and Altitude

When you buy specialty coffee, have you ever wondered how beans are sorted into grades like AA, SHB, or Screen 18? The answer isn't just about taste—it starts with physical traits like bean size and where the coffee was grown. These factors help roasters predict roast behavior and ensure consistency. But how exactly are those grades determined?

Coffee beans are graded primarily in two ways: by sieve size (mesh number) and by altitude (elevation in feet or meters where the coffee is grown). Size grading uses numbers like 15 or 19 to indicate the mesh size that a bean can pass through, while altitude grading uses terms like SHB (Strictly High Grown) or HB (High Grown) based on elevation.

Size Grading: What Do the Numbers Mean?

Coffee beans are sorted by physical size using a series of metal screens with holes of specific diameters. The size is indicated by a number representing the mesh—such as 15, 17, or 19. This number refers to the fraction of an inch that forms the hole diameter: for example, a '14' means the mesh has holes of 14/64 inches. The larger the number, the bigger the bean that can pass through.

Beans are categorized as small, medium, large, or extra-large depending on the mesh size they can pass. For example:

• 8 to 13: small to medium (common for peaberries)
• 12 to 29: standard to very large (typical for flat beans)

So, an SC-19 bean is one that passes through a 19/64-inch mesh. In general, the higher the number, the larger the bean. Flat beans are usually larger than peaberries, with flat beans ranging from screen 12 to 29, and peaberries typically between 8 and 13.

How Are Beans Sorted by Size?

The size-sorting process involves several mechanical and manual steps:

• Wet or dry processing to remove the coffee cherry’s outer layers
• Removing impurities such as stones, dust, and broken husks
• Using a winnower or air blower to separate beans by weight and density
• Manual or optical sorting to remove defective beans by color
• Passing beans through a series of metal sieves with progressively larger holes

The most common international sieve sizes range from 9 to 22, where each number equals the numerator of a fraction with 64 as the denominator. That means a '14' sieve allows beans that are 14/64 inches in diameter to pass. A designation like '19+' means the bean can pass through a 19/64-inch mesh or larger.

Altitude Grading: Why Elevation Matters

Coffee is also graded by the altitude at which it’s grown. Higher elevations typically produce harder, denser beans with more complex flavors. These are often graded with terms like SHB (Strictly High Grown), HB (High Grown), or EP (European Preparation).

For example, in some grading systems, HB denotes beans grown at 4,000–4,500 feet. While altitude grading systems vary by country, they consistently reflect how growing conditions affect bean density, cup quality, and roast potential.

Country-Specific Grading Standards

Different coffee-growing countries have unique grading systems based on bean size, defect counts, processing type, and altitude. Here are some examples:

Kenya

• AA Plus/AA: Screen 17–18
• AB: Screen 15–16
• PB (Peaberry): usually smaller than flat beans

Ethiopia

• Grading is based on defects per 300g sample:
• Grade 1: 0–3 defects
• Grade 2: 4–12 defects
• …up to Grade 8: over 340 defects (substandard)

Colombia

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

Brazil

• Type classification based on defects (e.g., Type 2 allows up to 8 defects, Type 3 up to 12, etc.)

Guatemala

• Grades include Strictly Hard Bean (SHB) at 1,600–1,700m and Hard Bean (HB) at 1,350–1,500m

El Salvador

• SHG (Strictly High Grown): above 1,200m
• HG (High Grown): 900–1,200m

Hawaii (Kona)

• Kona Extra Fancy: Screen 19, max 10 defects
• Kona Fancy: Screen 18, max 16 defects
• Kona Prime: no size requirement, max 25 defects

Jamaica

• Blue Mountain: Grade I (Screen 18), Grade II (Screen 17), Grade III (Screen 16)

Indonesia

• Grading based on 300g defect count:
• Grade 1: 11 defects
• …up to Grade 6: 151–225 defects

Why Does Grading Matter?

Grading ensures consistency in bean size, which helps roasters achieve even roasts. It also signals quality markers like altitude and defect rates, allowing buyers to assess cup potential and value. For specialty roasters, these grades guide purchasing decisions and help maintain high standards in green coffee selection.

Frequently Asked Questions

What does the number on a coffee bean grade mean?

The number (like 15, 17, or 19) refers to the mesh size in 64ths of an inch that a coffee bean can pass through. For example, a '17' means the bean fits through a 17/64-inch hole. Larger numbers indicate bigger beans.

What is the difference between flat beans and peaberries?

Flat beans are the normal two-seeded fruit of the coffee cherry, while peaberries are single, rounded beans formed when only one seed develops. Peaberries are often smaller, typically falling in sieve sizes 8 to 13, compared to flat beans which range from 12 to 29.

How does altitude affect coffee grading?

Higher-altitude coffee is often denser and of higher quality. Grading systems use terms like SHB (Strictly High Grown) or EP (European Preparation) to denote beans grown at specific elevations, usually above 1,200–1,500 meters, which tend to produce better cup profiles.

Why are defects important in coffee grading?

Defects—like insect damage, black beans, or underripe seeds—affect both the appearance and flavor of the brewed coffee. Grading systems (e.g., in Kenya or Ethiopia) count defects per 300g sample to determine the coffee’s grade and market value.

Do all countries use the same coffee grading system?

No. Each producing country—like Colombia, Guatemala, or Kenya—has its own grading standards based on local conditions. While many use similar metrics (like screen size or defect counts), the specific grades and terminology vary by region.

Recommended FrontStreet Beans for Size & Altitude Lovers

Explore FrontStreet Coffee’s Ethiopia Guji Huakui, a high-altitude lot with bright citrus and floral notes, grown at 1,900–2,100m and offering exceptional clarity. Pair it with Colombia Narino Supremo, a Supremo-grade coffee (screen >17) with balanced caramel and nuts. For something different, try Kenya Gikanda AB—screen 15–16 beans known for winey acidity and blackcurrant tones. All three showcase how size and altitude 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.