I am about 115lb and ordered a size small. These are very form fitted and tight. I like them that way so they don't roll down or move, but some may want to size up if just using for lounging!
I love these leggings so much. They are so flattering. I'm 5'8" and wear a size 10/12 and generally a Medium in Senita, but was torn on what size to get these in after reading reviews. I went with a Medium and they're perfect. I will own these in every color as soon as the green is re-stocked!
Seamless is the. way. to. go. These are so flattering. Love the compression and material. Please make more seamless designs and colors!
So I'm classically a small in nearly all Senita bottoms (5'5", 138 lbs, big butt and thighs, small waist). I bought the small green seamless leggings and still love them and wear them, but they are tight. I wanted to compare the mediums, so I did this in the gray and purple. I also love both of these, and wear them all the time. Honestly not a major size difference between the smalls and mediums, except a little more give in the leg so it's easier to put on. With all three, I find that the back dips down more than I'd like, but the front stays -fairly- high waisted (not as much as the lux pants/capris). So I'd give both the smalls and mediums a 99% for that reason- just a hair more high waisted and they'd be perfect! Obviously still a 5 star review, and I love and will keep all three pairs.