The foot has only one bone in the heel, which stays narrow throughout life. The front of the foot, in contrast, is made up of many bones connected by ligaments. This can increase the shoe size. The shoes you buy should be fitted to your longer and wider foot. Feet expand when bearing weight, so stand while your feet are being measured.
Feet tend to swell during the course of a day, so shop for shoes at the end of the day.
Never select a shoe by size alone. A size 8 in one brand or style may be smaller or larger than the same size in another brand or style. Buy the shoe that fits well. Don't assume that you will always have the same size feet. As you grow older, the size may change, so have your feet measured regularly.