If you're renting a watch with a metal bracelet, we size our watches 4 different ways:
To measure your wrist, use either a tape measure or a piece of string. If you don't have a tape measure, wrap a piece of string around your wrist where you'd like the watch band to rest. Mark the string where it completes one full length around the circumference of your wrist. Measure the string with a ruler, and repeat to confirm the accuracy of your measurement.