We measure our solid, continuous jade bangles by the inside diameter in millimeters. This is the size of a solid one-piece bangle that will slide over your hand/knuckles.
To find out what size bangle with slide over your hand/knuckles, collapse your hand/knuckles as best you can as shown in the photo. Please use a flexible measuring tape, ribbon, or strip of paper. Wrap it snugly around your hand/knuckles at the widest point (see image below). Here is a printable ruler PDF you can print out -- make sure you print it at 100% with no scaling.
Then measure the string/paper with an inch ruler. This is the circumference of your hand. Please take this inch measurement and multiply by 8. This is the inside diameter in millimeters of the bangle you need.
If your size falls in the middle, please round up rather than down to insure the bangle fits over your hand.
NOTE: Please consider the width of the bangle, as you may need a little larger bangle size for wider style bangles.