I bought a 2x and a 3x to make sure I had a good fit. I usually wear a 3x and have large arms. The 2x fit perfectly! I LOVE it! The best shirt I've ever worn. I use it as a jacket with short leave shirts or tanks in the summer. It's cool and works perfectly! PLEASE come out with more colors!  I always want this as a staple in my wardrobe, PLEASE. Never get rid of this style or this fabric. I love the slight stretch it has. And for those wondering, it launders wonderfully!! It doesn't shrink that I could tell when I washed in cold water and low heat for drying. It comes out without wrinkles if you hang it up right away. PERFECT! Thank you, thank you!!