I barely have a bum (although some may disagree) yet these were too tight to button. If you got any stomach or butt, definitely size up. I'm hoping to exchange these for an XL so we'll see. For reference, I am 5'7" and 194 lbs. Large bottoms usually fit well, but XL with this would have been better. Aside from that, nice material, not heavy (definitely not for super cold weather - would not keep you dry/warm ).