Extend a tape measure from the kneecap center to the top of the ankle. Note the measurement in inches.
Use the measurement to determine the appropriate shin guard size. Shin guards sold at sporting goods stores typically show length and age range on the packaging.
Try on the shin guards that fit the measurement and age range. Properly fitted shin guards should allow freedom of movement at the knee and the foot. If the shin guards restrict movement significantly, try the next size up or next size down. Shin guard manufacturers generally make shin guards in a variety of sizes depending on whether they will be used for baseball or fast-pitch softball and according to age range and player's height. In general, sizes for players under age 11 are 10.5 inches to 13 inches, also designated youth size; players 11-14 are 13 inches to 14.5 inches, designated intermediate/youth size; players 14-16 are 14.5 inches to 15.5 inches, designated intermediate/adult size; players age 16 to adult are 16 inches to 18 inches, designated adult size. In addition, shin guards come in single, double or triple knee styles that offer varying degrees of flexibility and movement. Umpire shin guards are typically 16 to 18 inches.