Coffee beans come in all shapes and sizes. Within the coffee market, we’ve defined the size by measuring the beans against a rounded inch. 20/64 of an inch is the largest screen size, and 8/64 of an inch is the smallest. In this range, you’ll find all the acceptable screen sizes in coffee.
Before the seller bags the coffee, the beans are poured into large screens, or sieves, with round one-inch holes that separate the coffee by size. Gravity does the rest of the work. Because the large beans stay in the upper screens and the small beans tumble down until and end up in a smaller screen sized sieve.