how to measure your kid:
(you can try it with a ruler, but it's a lot easier with a tape measure)

Chest: measure under the arms around the fullest part of the chest. Be sure to keep the tape level across the back and comfortably loose.

Waist: wearwoolf garments are cut pretty straight with a loose fitting (but not saggy) waist. Our waist measurements generally match the chest. 

Shoulders: measure across the top of the shoulders from one side to the other. 

Drop: measure from the middle underside of the collar down to the bottom of the hem.

Sleeves: measure from the tip of the shoulder to the end of the wrist.