Do it at home
What you'll need:
*A thin strip of paper
What you'll do:
*Take the strip of paper and wrap it around the base of your finger below the finger joint and close to the knuckle (where you would wear a ring).
*Mark the spot where the paper over laps and meets
*Measure the distance on your ruler and use the chart below to convert your measurement to your ring size.
*If your measurement falls in between a size, chances are you're a half size. If you are very unsure I'd recommend getting sized at a local jewelry store or purchasing a very inexpensive ring sizer from Amazon or Michaels.
International Ring Size Chart
All AVR ring sizes are listed in US and Canadian sizes
Band thickness matters
Thinner bands tend to fit true to size since they don't cover as much surface area. Thicker bands and wide split bands tend to fit snug since they cover a larger portion of your finger. See the images below.
Wide split band