How Coffee Growers Grade Raw Coffee Beans

When you buy specialty coffee, you trust that the beans were carefully picked and processed — but how exactly do producers decide which beans make the cut? One crucial step often hidden from consumers is green coffee grading. Whether you’re sourcing beans or just curious, understanding how beans are graded helps explain why some lots cost more, roast differently, or brew more consistently.

The short answer: most countries grade green coffee using one or a mix of three methods — by growing altitude, bean size (sieve size), or defect count — with some adding cupping scores or processing method into the mix. Each system aims to predict roast quality, cup potential, and market value based on measurable traits.

1. Altitude-Based Grading: Higher Elevation, Finer Beans

Many coffee-growing regions link bean quality to altitude. The theory? Cooler temperatures slow cherry development, allowing more complex sugars and acids to develop. These beans often have better density, which aids even roasting and produces a more stable cup.

Countries such as Guatemala, Honduras, El Salvador, and Mexico use altitude tiers to define grades. In Guatemala, for example:

• SHB (Strictly Hard Bean): grown above 1,350 m — the highest grade, denser and suited for full city to dark roasts.
• HB (Hard Bean): 1,200–1,400 m
• SH (Semi Hard Bean): around 1,000–1,200 m
• Lower tiers include EPW (Extra Prime Washed), PW (Prime Washed), EGW (Extra Good Washed), GW (Good Washed) for beans grown at 800 m and below.

So the higher the altitude designation, the more prized the bean — and typically the more vibrant and structured the cup profile.

2. Sieve (Bean Size) Grading: Bigger Isn’t Always Better, But Often Is

This method sorts beans by physical diameter using perforated metal screens measured in 1/64-inch increments. A “17/64 inch” hole equals a No. 17 sieve (about 6.75 mm), so a No. 18 sieve has slightly larger holes. The higher the sieve number, the larger the bean.

Larger beans are often more uniform in roast and can develop more complex flavours, though this isn’t universal. Ethiopia’s Yirgacheffe beans, for instance, are small but highly flavourful. Still, many origins rely heavily on sieve grading.

Notable examples:

• Kenya: uses AA++ (sieve 18+ or >7.15 mm), AA+, AA, AB. AA++ is the top tier.
• Colombia: simpler, with Supremo (80% beans must pass 17+ sieve) and Excelso (80% through 14/16 sieve, with ≤11% allowed through 14 sieve).

Peaberry beans (small, round mutant beans) have their own sizing standards, usually graded on 8–12 sieves.

3. Defect & Sieve Combination Grading: Counting Flaws Matters Most

Defects — broken, black, insect-damaged, or unripe beans — can ruin cup quality. To control this, many countries grade green coffee by the number of defects per sample and combine that with sieve size.

This method is especially common in countries prioritising specialty quality or facing complex production environments.

• Jamaica: grades beans using a mix of region, altitude, sieve size, and defect rate. For example, Jamaica Blue Mountain No. 1 must come from the Blue Mountain region, be grown above 1,700 m, pass through 18/17 sieve, and contain ≤2% defects (with a max of 4% across all grades).
• Brazil: the world’s largest producer uses multiple methods. Alongside sieve grading and defect counting, Brazil uniquely includes cupping tests. The six-tiered cup quality scale ranges from Strictly Soft (excellent balance) down to Rioy (harsh iodine notes), with the latter caused by beans absorbing soil odours in certain regions.

Defect counts are usually evaluated per 300 g or 350 g sample, with categories like black beans, sour beans, insect damage, and husks all counted toward the total allowable.

Frequently Asked Questions

What are the three main ways green coffee beans are graded?

The three primary methods are: 1) altitude-based grading (common in Central America), 2) sieve (size) grading (used in Kenya, Colombia), and 3) defect count combined with sieve grading (used in Jamaica, Brazil, Ethiopia). Some countries use a mix of these methods.

Does higher altitude always mean better coffee beans?

Generally, yes. Higher altitudes (e.g., above 1,200 m) tend to produce denser beans with slower maturation, leading to more complex sugars and acids. However, other factors like variety and processing also affect quality.

What does sieve size mean in coffee grading?

Sieve size refers to the diameter of green coffee beans, measured by the size of holes in a metal screen (in 1/64-inch units). A No. 18 sieve means beans must be at least 7.15 mm in diameter. Higher numbers indicate larger beans, which often roast more evenly.

Why do some countries grade coffee by defect count?

Defects — such as broken, black, or insect-damaged beans — can negatively affect roast consistency and cup quality. Counting and limiting defects helps ensure a more uniform and higher-quality green coffee lot.

Do all coffee-producing countries use the same grading system?

No. Grading methods vary by country based on climate, production style, and export priorities. While altitude, size, and defects are common factors, some regions add unique criteria like cupping scores or processing methods.

Are smaller coffee beans always lower quality?

Not necessarily. While larger beans are often preferred for uniform roasting, some origins — like Ethiopia — produce high-quality small beans with exceptional flavour profiles despite their size.

Recommended FrontStreet Coffee for Green Bean Analysis

Explore FrontStreet Coffee’s Kenya Little Tomato (AA grade, bright acidity, redcurrant and black tea notes) and Ethiopia Humbera (light roast, floral and citrusy, ideal for evaluating sieve-graded lots), along with Panama Humbera (complex, balanced, great for altitude-grade comparison). All three showcase how grading impacts cup profile. Freshly roasted within 5 days · Orders placed before 17:00 ship the same day · Next-day delivery across most of Guangdong Province.