To Size Gloves -
Measure the circumference of the part of your palm just below the knuckles, excluding your thumb (see image). Round up to the next whole inch, then add 1" to the measurement to determine your Keeper glove size. ie. 7.5" -> 8" + 1 = 9. Thus, 9 would be the Keeper glove size.
Measure both hands, and order the bigger size if they are different. Remember: Goalkeeping gloves should be worn big, generally 1/2" to 1" over the end of your fingertips.