To get the required size for your gloves, use a measuring tape. Make sure that you take the measurement around the hand joints (that is, where the diameter is the largest) while omitting the thumb and without tightening the tape - as illustrated in the image.
Size cm Inches
7 18 cm 7-inch
7.5-8 20 cm 7.5/8-inch
8.5-9 23 cm 8.5/9-inch
9.5-10 25 cm 9.5/10-inch
10.5-11 28 cm 10.5/11-inch
11.5-12 30 cm 11.5/12-inch
Note: If you hesitate between two sizes, always consider the bigger one.