Wrap a thin 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
Measure when hands are warm
Measure the exact finger the ring will be worn on
Check the size of a ring that already fits well
Use a ring sizer tool for the most accurate result
If between sizes, choose the larger size