Boys 8-14
Size 8 (M) 10 (L) 12 (L) 14 (XL)
Age (years) 6 to 7 7 to 8 9 to 10 11 to 12
Height (inches) 49-50 51-54 55-58 59-61
Chest (inches) 26.5 28 29.5 31.5
Waist (inches) 23.5 24.5 25.5 26.5

For accurate sizing, please follow these guidelines:
Height: Measure your child without shoes, feet together and back to the wall. Take measure from the floor to top of the head.
Chest: Place the tape measure under your child's arms and around the fullest part of his or her chest. Tape should be comfortably loose. 
Waist: Measure your child in his or her underwear. At their natural waistline, place one finger in between the tape and your child's body.