Since there isn't a sizing chart: I'm 5"2, 115 lbs, and ordered medium. Normally I'm in-between sizes S and M so I sized up and ordered an M just in case. It fits me nicely, but probably could have gone with a Small since I had to tighten the lace part quite a bit for it stay up.
Now onto the skort itself, it's amazingly cool and cute! The design looks like it comes straight out of a jrpg. All my friends loved it too! The material is nice as well.
Medium