Introduction:Gain an in-depth understanding of green coffee bean grading systems, from common screen sizes and altitude classifications to the grading standards and codes of major producing regions such as Kenya, Colombia, Brazil, and Ethiopia. This will help you master the skills for evaluating green bean quality—whether for import selection, roasting adjustments, or flavor prediction—enabling more precise decision-making.
The grading method of green coffee beans is one of the key factors that influence roasting performance and final flavor. Coffee-growing regions around the world have developed different grading systems based on their unique geographical conditions and market demands. These can generally be divided into two main categories: one is based on "screen size" to judge bean size, and the other is based on "growing altitude" to determine grade. Understanding these grading rules not only aids in quality control in bulk trade but also provides significant reference value for selecting and roasting specialty coffee beans.
First, let’s discuss the "screen size" grading method. This approach classifies beans according to the mesh size of metal screens—the larger the holes, the bigger the beans that can pass through. The screen number represents the ratio of the hole diameter; for example, a "18-screen" means the holes are 18/64 of an inch in diameter. Common screen sizes typically range from 9 to 22, where higher numbers indicate larger bean sizes. For instance, beans graded 19 and above are usually considered "large" or "extra-large," while those between 8 and 12 are typically small to medium. Peaberries (small, round beans), due to their differing shape and size, usually fall within screen sizes 8 to 13, while flat beans mostly range from 12 to 29.
Another common grading method is based on "altitude." Generally, high-altitude regions experience greater day-night temperature variations and slower growth rates, allowing coffee cherries more time to develop flavor compounds. As a result, coffee grown at higher altitudes often boasts richer acidity, aroma, and complexity. Different producing areas classify coffee beans into multiple grades according to altitude—for example, S.H.B (Strictly High Grown), H.B (High Grown), etc. The higher the altitude, the higher the grade typically is, and the price also increases accordingly.
The actual dimensions of screens are not expressed in intuitive millimeters or inches, but rather as "fractions of an inch over 64." For example, a "14" screen means the beans that can pass through it have a diameter no larger than 14/64 of an inch, and "19+" indicates the beans can pass through a 19/64 or larger screen aperture. Understanding the logic behind these numbers helps more accurately grasp the physical characteristics of the beans, which is useful for controlling roast heat, managing bean expansion rates, and ultimately influencing flavor expression.
Green coffee grading standards vary globally, with each country’s government or export association setting different regulations and codes based on local conditions. Below is a brief overview of the grading systems in some major producing regions:
In Africa, Kenya’s coffee grading is known for its rigor. Common grades include AA Plus-plus, AA Plus, and AA (typically 17 and 18 screens), as well as AB (15 and 16 screens). There are also PB (peaberry), C, and E grades. Ethiopia primarily grades coffee based on the number of defects, using a 300-gram sample as the basis—the fewer the defects, the higher the grade. The highest is Grade 1 (0–3 defects), and the lowest is Grade 8 (over 340 defects).
In South America, Colombia’s Supremo grade (greater than 17 screens) and Excelso grade (15–16.5 screens) are the most common export grades; UGQ (Usual Good Quality) refers to 12–14 screens. Brazil uses a system similar to COB (cupping-based defect count), grading beans from Type 2 to Type 6 based on the number of defects—the lower the number, the fewer the defects. In Central America, Guatemala is subdivided by altitude into grades such as Good Washed (700 meters), Extra Good Washed (700–850 meters), Prime Washed (850–1000 meters), and SHB (1600–1700 meters)—generally, the higher the altitude, the harder the beans and the greater the flavor potential.
El Salvador’s grading is divided into two main categories: washed and natural. Washed coffees include Central Standard (500–900 meters), High Grow (900–1200 meters), and Strictly High Grown (above 1200 meters), with different grade names for natural processed beans. Hawaii’s famous Kona Extra Fancy is 19-screen with no more than 10 defects, while Kona Fancy is 18-screen with up to 16 defects. Jamaica’s Blue Mountain coffee is divided into Grade I (18-screen), Grade II (17-screen), and Grade III (16-screen), with peaberries classified separately.
Indonesia’s grading is also primarily based on defect counts, using a 300-gram sample, and includes Grade 1 (11 defects), Grade 2 (12–25), Grade 3 (26–44), as well as Grades 4a, 4b, 5, and 6. The more defects, the lower the grade. Although this grading method is less intuitive than altitude or screen size, it still holds reference value for bulk trading.
In summary, whether judging bean size by screen number or evaluating flavor potential by altitude, the grading standards of each country reflect its local growing environment and market demand. For importers, roasters, or coffee enthusiasts, understanding these grading details allows for more accurate selection of green beans that meet specific needs, further enhancing overall quality and consistency from bean selection to brewing.
The above content is compiled by CoffeeHunters, a coffee news website.
