Definitely a size smaller (I had), my husband fits a large t-shirt (usually Gildan) and I bought him a medium size and it fits almost perfectly. maybe even a bit big.
AM Fitted T Shirt 3 Pack for Men's Clothing - T-Shirts & Tanks
46 Review
Ultimate Comfort and Style: Minus33 Merino Wool Ticonderoga Lightweight Men's Clothing, T-Shirts & Tanks
43 Review
Ashers Apparel Schrute Breakfast T Shirt Men's Clothing for T-Shirts & Tanks
34 Review
Men's XXL Super T Mockneck π from Lands End - Clothing, T-Shirts & Tanks
32 Review