As someone else that tends to be in-between medium and large sizes for t-shirts, I can relate to this. I think all of FAKKU's shirts are printed on American Apparel t-shirts, so you could get an idea of the fit if you have another t-shirt that's printed on an American Apparel t-shirt. American Apparel t-shirts tend to be slimmer than other brands, such as Gildan, so you might want to go for a large, but that's just my 2 cents.