METHOD 1: Use a ruler to measure the internal diameter of your favorite ring. Refer to the chart below for your ring size based on the ring diameter.
METHOD 2: Wrap a non-stretchy string around your finger where you'd like your ring to be worn. Make sure that the string is pulled snug to your finger. The tighter, the better to find your best fit.
Mark the spot where the end of the strings meet, and measure the distance with a runner in millimeters (mm).
Use the circumference column in above chart to find your size.