We built a simple aspect ratio calculator to help those that shy away from mathematical forumulas, or as I like to call them, everybody!
You will find many chain mail designers offering aspect ratios for their chains. This A.R. number will help you scale your chain up or down in thickness. Remember, 14 gauge is thick and 22 gauge is thin.
The calculator is simple to use. Type in the A.R. that you were given and it will calculate the size jump rings that should work. If your answer is 20ga 3.8mm ID, don't sweat trying to find that exact size, just round to the closest full (.0) or half size(.5). We are talking 1/10 of a millimeter and in most cases, this will not inhibit your success. Example: 20ga 3.8 would best be suited by 20ga 4.0. If your answer was 20ga 3.1mm, round down to 20ga 3.0.
I will also remind you that chain mail is a mixture of art and sceince. You may have to experiment to get the look that you want.