I bought the same size as another pair of leggings (m). They fit tighter than I imagined, but they feel great! Just what I needed for teaching spin class.
Super comfortable! The only thing that bothered me was it was a bit tight around my thighs at the bottom hem so I had to size up. So it looked like they were too small. It was a bummer because the previous size was perfect except for that! It still looks great though!