Chest: Measure from the bottom of one armpit seam across to the bottom of the other armpit seam. Double the number to get the actual chest size. 

Body Length: Measure from the top of the neck seam to the bottom of the garment. 

Size Chest Length
S 49" 28.5"
M 50" 29"
L 51" 29.5"
XL 52" 30"