How Specialty Coffee Beans Are Sized, Sorted and Graded

When you buy specialty coffee, you might assume all green beans are equal—but they’re not. Before roasters ever get their hands on those aromatic green beans, they’ve been sorted, screened, and scrutinized. The process determines not just quality, but price. So how exactly are coffee beans classified before they reach your bag? Let’s break down the steps from raw harvest to export grade.

The short answer: Coffee beans are first separated by size (usually screened through numbered sieves, often 10–20) and then by density using air or gravity tables. Most beans are flat on one side and semi-oval on the other, but exceptions like peaberries (small, round beans) and large maragogype beans are rarer—and pricier. Size grades like AA or SHB (Strictly Hard Bean) also play a role, especially in countries like Brazil and Ethiopia.

Why Size and Density Matter in Coffee Grading

Coffee beans are initially graded by size, typically using screens with numbered holes—common grades range from 10 to 20, where higher numbers mean larger beans. Some regions use letter grades instead, such as AA. The goal is to ensure uniformity, since evenly sized beans roast more consistently. However, even beans of the same screen size can vary in weight, and defective or shrunken beans may still slip through. Alongside size, density is critical: denser beans usually indicate higher elevation growth and better cup quality.

How Coffee Beans Are Sorted by Size and Weight

Sorting happens in two key ways. First, beans are passed through sieves or screens to separate them by physical size. Then, denser (and usually higher-quality) beans are separated from lighter ones using one of two methods: compressed air (manual jet separation) or gravity tables—elevated trays where a flow of air helps heavier beans fall to the bottom. Both techniques demand skill to use effectively. Properly applied, they remove underdeveloped or less dense beans that could negatively affect the roast and flavor.

Physical and Visual Defect Removal

Once sized and sorted by density, beans go through visual inspection to remove defects: broken, black, sour, over-fermented, or unhulled beans. This traditionally happens on moving belts where trained workers spot and pick out flawed beans. Other methods include electronic color sorting (mainly for Robusta) and older light-based techniques like the bichromatuc method. Despite technology, human eyes remain the most accurate tool today—though AI and automated systems may eventually take over.

Global Coffee Grading Systems and Export Grades

Different countries use different classification systems. Some, like Haiti’s, are overly complex with little practical impact. Others, like Brazil’s, rely on intricate but necessary machinery. Generally, there are six main export grades. At the top is SHB (Strictly Hard Bean) or sometimes called Highland Coffee, grown at elevations above 1,200 meters (or 4,000 feet)—often translated from a base of 400 meters in some local systems. These beans are denser and typically produce brighter, more complex cups.

Why Roasters Prefer to Buy Green, Not Roasted

Before coffee reaches consumers, roasters nearly always buy green beans and roast in-house. There are two main reasons. First, once roasted, coffee has a very short shelf life due to rapid staling—flavor compounds degrade quickly after roasting. Second, most retailers in the Americas and Europe prefer sourcing freshly roasted beans locally. This gives them better control over roast profiles and final cup quality, ensuring the coffee meets specialty standards.

Frequently Asked Questions

What does it mean when coffee beans are graded by size?

Coffee beans are graded by size using numbered screens (often 10–20), where a higher number indicates a larger bean. The beans are passed through sieves to separate them by width. Some regions use letter grades like AA instead. Uniform size leads to more even roasting, though weight and defects also affect final quality.

Why are some coffee beans denser than others?

Density often correlates with growing altitude. Higher-altitude coffee cherries ripen more slowly, producing denser beans with more concentrated flavors. Dense beans usually roast more evenly and are considered higher quality, especially in specialty grading systems.

How are peaberry coffee beans different?

Peaberries are small, round beans that form when only one seed develops inside a coffee cherry, instead of the usual two. They’re less common, usually rounder than flat beans, and often have more concentrated flavor. Because of their rarity, they typically command higher prices.

What is SHB coffee and why is it special?

SHB stands for Strictly Hard Bean, referring to coffee grown at high elevations—commonly above 1,200 meters (around 4,000 feet). These beans are denser due to slower growth, leading to a more complex and brighter cup profile. In some systems, this equates to a base elevation of around 400 meters.

How are defective coffee beans removed during processing?

Defective beans—such as black, sour, broken, or over-fermented ones—are removed through visual inspection, often on moving belts. Other methods include electronic color sorting and light-based defect detection (like bichromatuc), but human eyes are still considered the most reliable method for spotting flaws.

Why don’t specialty roasters buy pre-roasted coffee?

Specialty roasters prefer to buy green beans and roast themselves because roasted coffee stales quickly, losing aroma and flavor within weeks. Roasting in-house ensures freshness and allows control over roast levels. Most retailers also prefer sourcing roasted beans locally for better quality assurance.

Recommended FrontStreet Coffee for Single-Origin Exploration

Try FrontStreet Coffee’s Yirgacheffe and Ethiopia Humbera for bright, high-grown profiles that exemplify SHB-grade qualities. The Yirgacheffe offers floral and citrus notes ideal for pour-over, while the Ethiopia Humbera highlights juicy berry tones perfect for exploring delicate, high-density beans. Both are grown at elevation and showcase why size and density matter in specialty grading. Freshly roasted within 5 days · Orders placed before 17:00 ship the same day · Next-day delivery across most of Guangdong Province.