Here's how we measure our t-shirts. Try checking the size of one of your own t-shirts to get an idea of how ours will fit.
The width is measured from pit to pit and the length from shoulder to bottom hem
Medium: Width 51cm x Length 72cm
Large: Width 56cm x Length 77cm
XL : Width 61cm x Length 80cm
All our tees are standard unisex t-shirts and the size may vary slightly from brand to brand.