Typically, incontinence pants for women are the same size as the underwear you would buy normally. The measurements will be available on the product description or any label attached to the panties. If you want to get an accurate measurement for your underwear, take a measure and draw it from the middle of one hip bone to the other hip. Then, times that number by two. This should tell you what size of incontinence panties will fit comfortably.
Remember, sizing is important. If the panties are too big, you may leak through. If they are too small, they are going to be uncomfortable.