Gather a ruler or measuring tape, a sheet of paper, and a pen or pencil
Place the paper on a hard, flat floor against a wall
Stand on the paper with your heel touching the wall
Keep your weight evenly on both feet
Mark the longest point of your foot on the paper
Measure the distance from the wall edge to the mark
Repeat for the other foot
Use the larger measurement
Measure in the evening for the most accurate size
Compare the measurement to a shoe size chart