A ring that is too loose or too tight is uncomfortable to wear or may be easily lost. With four different ring sizing systems in use worldwide, determining a ring’s actual size isn’t always straightforward. If you have a ring you want to sell, or if you want to buy one that fits as well as a ring you already have, take the time to measure carefully.
Cut a strip of paper 1/2 inch wide and 3-1/2 inches long with scissors.
Wrap the paper strip into a circle and place it on the inside of the ring. Let it unroll and adjust it until it fits snugly against the inner surface of the ring.
Make a mark with the felt-tip pen at the point where the paper overlaps itself.
Remove the paper strip from the ring and unwrap it. Lay it down on a flat surface.
Measure from the end of the paper to the mark. A measurement in millimeters will give you greater accuracy, but most ring size charts include measurements in inches as well.
Compare the measurement to a chart that classifies the ring size standards in your area.