Be sure to measure your feet before you go shoe shopping to ensure a good fit. It’s best to measure them in the afternoon or early evening, after you've been walking on them for a few hours, because they expand throughout the day. Also, be sure to stand while you're taking your shoe measurements to get accurate results.

Trace your foot: Place a piece of paper on a hard floor. While wearing socks of normal thickness, place one foot on the paper. Stand and bend your leg slightly forward so that your shin is in front of your ankle. Using a pencil, trace the outline of your foot.
Mark the length and width: Use your pencil to draw straight lines touching the outermost points at the top and bottom of the outline, then both sides of the outline. You should have a box-like diagram.
Measure the length and width: Measure the distances between the horizontal points that show your foot’s length using a tape measure or ruler. Write down this number. Repeat this step for the vertical points that show your foot’s width. Again, write down this number. Repeat these steps for your other foot, and use the larger measurement of the two.
Find your shoe size: Subtract two-tenths of an inch from each of your numbers to account for the space between your foot and the pencil line. These final numbers are your foot measurements.
U.S. vs. European shoe sizes: Once you determine your U.S. shoe size, you can determine your approximate European shoe size.