Wrap a strip of paper or string around the base of the finger
Mark where the ends meet
Measure the length with a ruler in millimeters
Compare the measurement to a ring size chart
Measure the finger at the end of the day for best accuracy
Make sure the paper or string is snug but not tight
Measure the same finger more than once to confirm
If between sizes, choose the larger size
Use an existing ring that fits well and measure its inner diameter
Match the inner diameter to a ring size chart
Visit a jeweler for a professional sizing