Method A How to Measure Ring Finger Size Step 1 Get a nonstretchy string or paper about 6 (152MM) long and 1/4 (65MM) wide Step 2 Wrap around the base of your finger It has to fit snug, but not too tight Step 3 Mark the point on the string/paper where it overlaps forming a circleTo properly measure your ring size you'll need the following items Either a) a piece of thick string or b) cotton piping cord measuring at least 30cm / 12 inches in length If you go for a cord try to find one that's quite thick, ideally around the same thickness as the back ring you intend to buy, though one that's slightly thinner will3 Mark where the string ends with the pen 4 Place the measured string on the ruler with the area marked on your right 5 The number closest to the pen mark is the circumference of the ring in millimeters 6 Use the ring size chart above to translate the measurements into a ring size How do i measure my ring size in mm