Normally I wear size S for Nike leggings. For the most part, it fits true to size but the problem was with the waistband being extremely tight. I sized up to size M and found it felt as snug as my usual size S leggings. Aside from the waistband, the leggings are comfortable and have a barely-there relaxed feel. The detailing on the leggings can be subtle, but in good lighting or in the sun they look really cool and stand out.