Selecting the perfect-sized watch is essential for both comfort and style. If a watch is too big it will slide around on your wrist and be uncomfortable. If a watch is too small it will look out of proportion and feel constricting. Detroit watch companies offer a variety of sizes to fit any wrist size. To find your perfect fit, follow these simple steps: Use a flexible measuring tape (or a string that you can mark) to measure the circumference of your wrist where you would like to wear your watch. If using a string, lay the string flat on a ruler next to see how long it is in millimeters (mm). This is your wrist size.