Here you will find explanations to terms used in chainmail. You don’t need to know these, but it may help in your search for the right rings for your project.

ID stands for inside diameter
OD stand for outside diameter

Aspect Ratio (AR)

Is a number used to give you an idea on how lose or tight a chainmail weave will be.
You get this number but dividing the ID of the ring by the wire diameter(WD). So ID / WD = AR.
For example, a ring with an ID of 1/4 with a WD of 1/16th would give an AR of 4.
As long as you use the same units, this will work. So all numbers used can be decimal, fractional or metric.
The bigger the number, the looser a weave will be, and the smaller the number, the tighter it will be. There is no one best AR number. Some people like their weave tight, while others like it looser; it’s very much a personal preference.
AR can help you if you want to change wire size while still keeping the same tightness of the weave.
Let’s change our wire from 1/16 to 1/32. We want to use the same AR of 4. Let’s rearrange the formula a little: 4(AR) x 1/32(WD) = 1/8(ID).
As you change your wire size or ID of your rings, you will probably get ARs that are not whole numbers, like 4. I’ve found it better to do the math in decimal or metric.