I wear a size 10 in pants and shorts and that usually means a size large in sweat pants and pajama pants. I usually get a size XL in any lounge pants just to be comfortable. With this specific brand I usually order a size smaller than normal (medium) because the legs are always so big. From the pictures these specific sweats didn't look like the bottoms were flared so I ordered my normal size large and I'm glad I did because these fii absolutely perfect. I suggest ordering your normal size because these are not flared or oversized. Fir reference I am 5'6 and weigh 155-160 pounds. I left a couple pictures hope they help you make a decision on size.