The way womens' pants are measured can be quite confusing if you don't know the simple trick to converting between mens' and womens' pants sizes.
Womens' pants sizes are the waist size minus 21. So to convert from womens' to mens' you add 21.
A woman's size 10 pair of pants would be equivalent to a men's size 31, in the waist; the inseam is measured the same for both men and women.
There is some room for error either way here so take your build into consideration. If you have fuller hips and rear you may need a size slightly bigger and if your hips are slim or your rear end is flat then you may need a little smaller.
Be honest and you'll save an exchange. Men's jeans are not cut as full in the hips as women's so keep this in mind. That is why sometimes this conversion comes out bigger than your waist is. Remember though you have to fit the biggest part whether it's the waist, the hips, or the rear.
Here's how to find the best pants for your body shape shared by Glamour.com.