I am 5'9" and weigh about 150, I ordered a Medium and it is a perfect fit! I have bought 2 shirts that are the same style from Patti Boutique for twice as much,  I love the Patti brand and was afraid to give this one a try because I assumed it would be poor quality but I was way wrong! They are literally the exact same shirts but half the price! The material is soft and stretchy and the color is beautiful! I will be buying one in every color!