The coffee beans, after milling are graded mechanically into various grades which differ in size, weight or shape. Incorporated into the grading system are the colours sorting machines which are the capable of separating high quality coffee beans from light and defective ones electronically.
In Kenya grading mechanism the resulting grades are roughly described as follows:

E
This is the largest of all the grades in size and has been named Elephant grade in the grading. Usually there are two seeds joining together to form the seed in a single cherry. It is the source of ears when the seeds part during handling. This grade also includes the very large PB beans. Like PB this grade is normally in small quantities in a consignment.

AA
This grade has good size formation of large beans (7.20mm screen). This grade usually fetches a higher price than any other grade.

AB
This grade is a combination of two grades A and B A- 6.80mmscreen, B-6.20mm screen. AB is regarded as a representative of the other grades in a consignment and usually there is more coffee of his grade than of other grades in a consignment. It is also a popular grade which fetches good prices.

PB
Round beans which usually grow as one bean in a single cherry bean. About 10% of coffee falls in this grade.

C
Smaller beans than B and most of the thin beans in this grade.

TT
This grade is composed of light beans which are raged and are usually separated from all other grades.

T
The smallest and thinnest beans, most of the beans are in the form of chips. Most of the beans in this grade are broken and faulty. In classification, this grade is always below the other grades.

MH /ML
This is the coffee that has not gone through the wet processing either because it was not picked, or because it fell from the trees after ripening. About 7% of total crop falls into this grade, which generally fetches lower prices and which has sour tasting liquor.

The above grades are then subjected to a vigorous classification by liquoring Department of the board to assign the classification standards as to the quality of the raw roasted and cup taste. The cup quality is usually described as fine fairer to good, fair to average quality down to common plain liquor. Coffee of good raw quality and appearance and has a good roast also has a pleasant flavor.

Sl No.
 Grade
 General description
 Screen apertures as per KS 174 or ISO 415-1980*
 
i)
 E
 Elephant – (Retained on 21)

Two beans joined together, it is a genetic defect. And includes very large (bold) AA
 Size diameter 8.3 mm
 
ii)
 AA
 Flat beans - (Through screen 21 retained on 18)
 size diameter 7.2 mm
 
iii)
 AB
 Flat beans - (through screen 18 retained on 17)
 Size diameter 6.35 mm
 
iv)
 PB
 Pea berries - (through screen 17. Retained on 12)

One ovule develops instead of the usual two
 Size diameter 4.76 mm
 
v)
 C
 Smaller beans - (through screen 16 retained on 10)
 Size diameter 3.96 mm
 
vi)
 TT
 Light density beans, from AA, AB and E grades by air extraction
 
 
vii)
 T
 Smallest, consists of brokens and small C (through screen 7 )
 Size diameter 2.9 mm