It runs smaller.
Order 2 sizes up. I am 5'2, 120lbs. I usually wear a small or medium. I had to exchange size 4 to a 6 and the 6 its still pretty snug. I think size 8 would of been a perfect size but I didn't feel like doing another exchange. I do love Spyder gear clothing they have them most high quality products. The sizing is just a little tricky.