Wrap a strip of paper or a flexible measuring tape around the base of the finger
Mark where the ends meet
Measure the length of the strip in inches with a ruler
Use the measured circumference in inches as the ring size reference
Compare the measurement to a ring size chart that lists sizes in inches
Measure the finger at the end of the day for the most accurate result
Make sure the strip fits snugly but not tightly
Measure the same finger more than once for consistency
If the knuckle is larger, measure both the knuckle and the base of the finger
Use the larger measurement if the ring must pass over the knuckle