Here's a short video on narrowing the leg that you'll likely find beneficial.
Using a pair of existing pants that you know you like the leg width of helps with determining what the finished hem width should be. Much also depends on what style of pant you're designing and what looks best on your body.
The wider you are in your hip area and the tighter you want the legs of your pants to be, the more you risk giving the impression of an inverted triangle which will simply emphasize your hip circumference.
I'll close with a word of caution, don't over 'narrow' those legs.