1. Measure your wrist with a cloth or paper measuring tape snugly below the wrist bone.  If you don't have a soft measuring tape you may also use a piece of string or ribbon, wrap it around your wrist just below the wrist bone and cut the string where the ends meet.  Take the piece of string and measure it with a ruler.   
2. This is your WRIST size.

Standard wrist size for female is 15 to 16 cm

Standard wrist size for male is 16.5 to 18 cm