Unisex sweatshirt sizes - UK?

courtxoney

i was looking into buying a sweatshirt online and it's from the UK.
it's a unisex sweatshirt (doesnt say if it's cotton or anything) and only comes in sm, med, lg and xl.

US sizes i usually wear a medium, so it's not too tight but not too baggy.

would anyone be able to help me on what size you would suggest i should get?