Slipper. Footwear Sizing Guide - If you are unsure which shoe size to purchase, please follow the following steps: Draw a straight line, longer than your foot, on a piece of paper. Place the paper on a flat surface. Stand on the line with your heel and longest toe centered on the line. If measuring a child's foot, it may be easier to hold the paper up to their foot. Place a mark on the line at the tip of the longest toe and at the back of the heel. Repeat steps 1-3 for the other foot. Measure the distance between the marks. Taking the larger of the two measurements, use the conversion chart to find your correct shoe size.