Wrap a strip of paper or string around the base of your finger
Mark where the ends meet
Measure the length with a ruler in millimeters
Compare the measurement to a ring size chart
Measure the same finger at the end of the day
Measure when your hands are warm for the most accurate fit
Make sure the strip fits snugly but not tightly
Measure the finger you will wear the ring on
If between sizes, choose the larger size
Use an existing ring that fits and measure its inner diameter
Visit a jeweler for a professional sizing