Put on the socks you are planning to wear for wrestling. Sit down on a chair, then place your foot on a blank sheet of paper on the floor in front of your chair. Trace around your foot with a pencil.
Measure the distance between the two farthest points of the foot trace, then deduct 1/5 inch to determine your foot length. Then measure the distance between your two widest spots, and deduct 1/5 inch for the total foot width. Use these numbers to check the manufacturer's shoe size tables, to predetermine your approximate size in wrestling shoes. If needed, convert the inches into centimeters by multiplying the measurements by 2.54.
Try on a pair of wrestling shoes, lace them up and stand up to check the fit. Wrestling shoes are sized right, when they fit snugly around the heel and arch, while allowing for some room in the front. You will probably have to go up at least a half size from your regular street shoe size. You should be able to wiggle your toes comfortably.
Consider your material of choice and the give you can expect from it. All wrestling shoes will stretch to some extent during the breaking-in period, and you need your shoes to still fit snugly afterward. While you don't want them to be too tight, loose wrestling shoes won't give you the support you need and may cause injuries.