I'm 5-7 and usually wear 32" jeans, which have room around my waist but if they are a tighter fitting design, they tend to get a bit familiar with me since I'm a bit....em, I'll say muscular below the waist. Medium ski pants fit me well but could use a bit more room. Medium snowboard pants fit great. With both, I take over an inch off the waist with the velcro waist straps while my base layer shirt is tucked in. So if you have thin legs and flat but, you could probably do well with a small. If you can, hit a local store and try on a few.