O'neill T-Shirt Sizing
Mens' Tops Chest (inches) Chest (cm)
S 36.5 - 38.5 93 - 98
M 38.5 - 40.5 98 - 103
L 40.5 - 42.5 103 - 108
XL 42.5 - 44.5 108 - 113
Boys' Tops Chest (inches) Chest (cm)
S (8) 26 - 27 66 - 69
M (10 - 12) 28 - 29 71 - 74
L (14 - 16) 30 - 31 76 - 79
XL(18-20) 32 - 33 81 - 84
See our complete fitting guide here