Introduction:Have you ever wondered why coffee beans from different origins carry various grade designations? From Brazil’s NO.2 to Kenya’s AA, these labels actually reflect a rigorous grading logic. This article will delve into the grading systems of major global coffee-growing regions, including the three main evaluation methods based on altitude, screen size, and defect rate, while also introducing Brazil’s unique cupping and deduction system. Mastering this knowledge not only helps you accurately select high-quality coffee beans but also enhances your understanding of coffee flavors.
When you hear a café owner mention “we use Brazilian Santos NO.2” or “this is Kenyan AA-grade coffee,” it actually involves a complex and location-specific international coffee grading system. Due to vast differences in terrain, climate, and cultivation practices across producing regions, coffee-producing countries around the world have developed their own unique quality evaluation methods. Understanding these grading standards is an indispensable skill for any coffee enthusiast or industry professional when selecting green beans.
Currently, the mainstream methods for grading coffee beans can be roughly divided into three categories: based on growing altitude, based on green bean screen size, and a comprehensive evaluation method combining screen size and defect rate. Additionally, major coffee-producing nations like Brazil also employ cupping assessments for fine-grained grading to ensure consistency in export quality. These standards not only affect coffee pricing but are also directly tied to the final flavor profile.
First, altitude is one of the key factors influencing the flavor and quality of coffee beans. Generally speaking, higher-altitude regions have cooler temperatures, causing coffee cherries to ripen more slowly, resulting in denser internal bean structures, pronounced acidity, and rich complexity. For example, Guatemala classifies coffee grown above 1,350 meters as SHB (Strictly Hard Bean), considered the country’s highest grade, while Mexico’s SHG (Strictly High Grown) requires beans grown at altitudes above 1,700 meters. Coffee from such high-altitude regions typically boasts brighter acidity and complex aromas, making it highly favored in the specialty coffee market.
Second, many African and South American coffee-producing countries use “screen size” as the basis for grading. Screens refer to metal plates with fixed-size holes, measured in 1/64-inch increments. For instance, a size 17 screen has a hole diameter of 6.75 mm, and beans that can pass through this screen are classified as size 17. The larger the screen number, the bigger the bean size, which is generally associated with greater flavor potential. Top-grade coffees from Kenya and Tanzania, such as Grade AA, must pass through size 18 (approximately 7.14 mm) or even larger screens; Colombia’s Supremo grade requires passing through a size 17 screen or higher, while Excelso may include a small proportion of smaller beans.
Lastly, and most complex, is a grading method that comprehensively considers both screen size and the ratio of defective beans, supplemented by cupping assessments. Take Brazil as an example—its grading system combines defect deductions, screen numbers, and cupping results into a unique “three-tiered” evaluation framework. Brazilian coffee grades range from NO.2 to NO.8, with NO.2 being the highest grade, indicating the lowest defect rate, and NO.8 representing the lowest commercial grade. If a 300g sample of green beans contains fewer than 4 defects, it can be classified as NO.2, but beans with zero defects are extremely rare, so a NO.1 grade effectively doesn’t exist in practice.
Brazilian coffee beans are also labeled with screen sizes—for example, size 19 indicates a bean diameter of approximately 7.54 mm. This value applies only to flat beans; peaberries use a separate oval-hole screen (sizes 8–13). In addition, Brazil uses cupping results for flavor grading, divided into six levels, where “Strictly Soft” is the highest, indicating an excellent balance of sweetness, acidity, and body. Grades 5 and 6 may exhibit noticeable iodine or off-flavors, often related to soil conditions or processing environments in those regions.
Interestingly, to maintain the accuracy of cupping, Brazilian certified Q graders must adhere to extremely strict lifestyle regulations—including avoiding pungent foods like garlic, onions, and leeks, as well as abstaining from alcohol, tobacco, or strong perfumes—to prevent interference with taste and smell perception. Though unique, this system reflects Brazil’s high regard for quality control as the world’s largest coffee exporter.
In summary, whether based on altitude, screen size, or defect rate, each country’s coffee grading system is grounded in scientific rationale and practical necessity. For consumers or buyers, understanding these grading principles helps you make smarter choices when selecting high-quality coffee beans—whether you’re brewing pour over at home, using filter packs, or running a café. This knowledge forms a crucial foundation for elevating flavor quality control.
The above content is compiled by CoffeeHunters, a coffee news website.
