We have  created a Ring Sizing Chart.  You can not trust your computer screen as web browsers can be easily zoomed in and out, offering you sizes that are not accurate.

Download our Jump Ring Sizing Chart
and print it out.  This will give you a better estimate of true ring size. 

Two things to remember:

Ring Thickness or Gauge - the lower the number the thicker the ring

We use I.D. Inside Diameter to measure rings.  Craft stores often use O.D. Outside diameter.  Each product description will give you both values.