If you have XL in t-shirts, you will get 2X. because they are snug and fit well. The material is light, silky, but now thin, like silk. My son looks really good in it. If you have L in your shirts then go for Large, if you don't have a belly and if you have one then go for XL. The material stretches a bit, son says it's comfortable. The shirt is a good length so it can be tucked in or untucked at your choice.