Our clothing comes in a 'swing easy' fit - semi fitted but with enough room to swing freely. The sizing for the golf shirts and t-shirts is identical. So if you are a medium in a t-shirt you will be a medium in a golf shirt. Small: 36-38" Medium: 38-40" Large: 40-42" X Large: 42-45" XX Large: 45-49" XS (8): 32" S (10): 34" M (12): 36" L (14): 38" XL (16): 40" If the size is wrong we have a free returns policy. Simply post your item back to us using your pre-paid returns sticker and we will exchange the item or provide you with a refund.