Finding the perfect shoe size is essential to foot health. Not only is the right shoe size necessary to promote healthy circulation in your feet, a shoe that is too big could cause you to trip and fall. Since you can't try shoes on if you're buying them from an online retailer, knowing your proper size is one way to guarantee you buy the best-fitting shoe.
Download a shoe size printout from an online shoe retailer. Make sure the chart you download is sex and age appropriate, as each chart will vary.
Print the chart out. Since it will most likely print on two pages, trim away excess paper and tape the two pieces together where the lines meet.
Lay the printout chart on a flat, stable surface and place your bare foot against the heel edge. You may wear socks while doing this, but do not wear shoes. This will give you an inaccurate size reading.
Mark with a pencil the point on the chart where the end of your big toe reaches.
Step off the chart and look at the line. The number just over the line is your shoe size. For example, if your toe rested above the 8, but just below the 9, a size 9 is your best fit. If it rested below the halfway mark, an 8 1/2 will do.