T-Shirt

S: Chest 51.5cm / 20¼" Length 69cm / 27¼"
M: Chest 53.5cm / 21" Length 71cm / 28"
L: Chest 56.5cm / 22½" Length 73.5cm / 29"
XL: Chest 59.5cm / 23½" Length 74cm / 29¼"

Sweatshirt

S: Chest 50cm / 20" Length 69cm / 27¼"
M: Chest 53cm / 21" Length 71cm / 28"
L: Chest 56cm / 22" Length 74cm / 29¼"
XL: Chest 59cm / 23½" Length 74cm / 29¼"

The best way to check what size you need is to measure a t-shirt you already own.

Chest measurement is from one armpit to the other. Length measurement is from the highest point on the collar to the bottom seam.