There are two ways to use a printed ring size chart. The first way is to directly compare the ring to the printed circles and choose the closest one that fits. The second way is to measure the circumference of your finger and locate the ring size on the chart.
Before printing out a ring size chart, be sure that the printing options do not shrink or stretch the chart when using the circle comparing method. To be as accurate as possible, print out different charts from different sources and compare them.
Select a ring that needs to be sized and place it on top of a circle. The circle should match the inside frame of the ring. If it is too big, select a smaller circle, and vice versa, until the closest circle is found. Whatever number that circle is labeled with is the ring size.
The other method is using a string or measuring tape to measure the ring finger's circumference. Locate the number on the printed chart and determine the best ring size for that circumference.