Place a sheet of paper on a hard floor against a wall
Stand on the paper with your heel against the wall
Keep your weight evenly distributed on both feet
Mark the tip of your longest toe on the paper
Measure the distance from the wall to the mark in inches or centimeters
Repeat for the other foot
Use the larger measurement to determine your shoe size
Compare the measurement to a shoe size chart
Measure your feet at the end of the day for the most accurate fit
Wear the socks you plan to use with the shoes when measuring
Leave a little extra space for comfort and toe room