Making the grade: coffee sizing and grading

Quakers, taints, and faults? If you are a coffee lover and these terms have little meaning for you, you are in the right place! Coffee classifications can be maddeningly complex when you are unfamiliar with the terminology and delightfully simple once equipped with the lexicon. In our Bean Basics blog, we cover the difference between Arabica and Robusta beans. In this blog, we are focusing solely on the classification and grading of the Arabica coffee. The first step in coffee grading is determining the coffee’s screen size.

While beans of any size can be delicious, larger beans are associated with higher quality as they have a longer maturation period which often leads to more flavorful beans. To determine a bean’s size, prior to roasting, all beans pass through perforated sieves with holes of increasing diameter. Beans with screen sizes of 16 or 18 (they pass through a sieve with 16/64″ or 18/64″ diameter holes) are generally considered the highest quality in terms of size. After the beans are sorted into their size bracket, they are collectively evaluated on appearance and attributes. Coffees with the greatest uniformity and cleanliness earn the highest grade. The first phase of the attributes test is a visual scan; the second phase involves roasting and evaluating the beans for defects.

Defects can take the form of physical defects, of taste, texture, acid level, or aroma defects, faults (off-color, irregular shape, etc.), and taints (a sour flavor generally resulting from poor storage or over fermentation). A full list of defects is included at the end of this entry. To achieve Specialty Grade Coffee status, Grade 1, a 300-gram coffee sample must have beans +/- 5% of the same screen size, no primary defects, 0-3 secondary defects, 0 quakers (unripe beans), and a distinct unifying attribute be it taste, acidity, body, or aroma. At The Queen Bean, we only purchase Specialty Grade Coffee.

Premium Grade Coffee, classified as Grade 2, is similar to Grade 1 coffee but allows for 3 quakers and 0-8 secondary defects. Grade 2 coffee is the most widely available high-quality coffee and is often found in cafés and coffee shops.

Exchange Grade Coffee, classified as Grade 3, has at least 50% of beans above screen size 15 and a maximum of 5% below screen size 15. The beans must be free from faults, may exhibit 9-23 secondary defects, and 5 quakers. Grade 3 beans are most commonly used for supermarket brands and by non-specialty coffee producers.

There are two more Grades but we suggest you stay clear of them! Grade 4 is referred to as Standard Grade Coffee (24-86 secondary defects allowed) and Grade 5 is referred to as Off Grade Coffee (86+ secondary defects allowed). In our experience, Grade 4 and 5 beans are extremely sour and unpleasant to drink.

We hope this gives you a better understanding of what you are drinking when you see numbers and grades listed next to your coffee. If you see the words “Specialty” or “Premium”, order with the assurance that your beans have been put to through a rigorous evaluation and made the grade. Check back next week for our blog on coffee varietals.


Defects list

Primary Defects

Primary Defect Number of occurrences equal to one full defect.
Full black


Full sour




Large stones


Medium stones


Large sticks


Medium sticks


Secondary Defects

Secondary Defects Number of occurrences equal to one full defect






Insect damage


Partial black


Partial sour






Small stones


Small sticks


Water damage


Tables credited to

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