To start, make sure you’re either barefoot or wearing the socks you intend to wear with the shoe. Next, place a piece of paper on a flat, hard surface, and step your foot firmly onto the piece of paper. Keep in mind that your full weight should be on the foot you are measuring. Lastly, use a pencil or a ballpoint pen to trace your foot, keeping it at a 90 degree angle to the piece of paper. Repeat the process for your other foot. Tip: Measure in the evening, when your foot is at its fullest shape.