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How to control the fit of your chain mail weave

Use the Aspect Ratio equation to choose the right jump rings for your project
This image is probably not to scale, depending on the type of screen you are using to view Facet. But if you study the rings, you can see that the inner diameter can be the same even when outer diameter is different, depending on the gauge of the wire. 

Aspect Ratio (AR) sounds intimidating because, let’s face it, it’s math. But conquer this one simple formula, and you’ll have complete control over the density of your chain mail work. Do you want an open and airy version of a Byzantine link, or do you like the look of a tightly woven chain? The following information will guide you on the correct choice of jump rings. 


Essentially, calculating Aspect Ratio (AR) means figuring out how many jump rings each jump ring can comfortably hold. The math is based on the relationship between the ring’s inside diameter (ID) and the thickness of the wire that makes the ring. 

Why use a jump ring’s ID in the formula instead of its outside diameter (OD)?  Because, as seen below, a 5.5 mm ID jump ring will have the same ID whether it’s made of 16- or 20-gauge wire, but its OD will be different.

So, here’s the formula to find AR:

ID ÷ gauge = AR

Basic math: If ID and gauge are equal, the ratio is 1, which means that one jump ring threaded through a second would completely fill the second jump ring. The greater the AR, the more space there is for additional rings, so the weave is looser.


If you’re buying premade jump rings, the supplier will tell you the ID and gauge of your jump rings. 

In the United States, the American Wire Gauge (AWG) scale, also known as the Brown & Sharpe (B&S) gauge, is most commonly used to measure wire thickness. 

The ID is usually given in millimeters. But there’s a caveat, called “springback.” Most manufacturers base ID on the size of the mandrel that the wire was coiled around when the jump rings were made. But when that coil is cut into jump rings, the rings tend to “spring back” slightly, so the actual ID of the rings is slightly larger than the mandrel’s diameter. 

The degree of springback varies with the hardness of the wire. The most reliable way to calculate your ID: Use digital calipers to measure the ID of 10–15 rings from your stash and find the average.


Before you can plug numbers into the AR formula, convert the ID and gauge to the same measuring system. I convert both into inches, but metric works just as well. The key conversion equivalent is: 

1 mm = 0.0394 in. 

To find the inch measurement for your wire gauge, measure the wire with digital calipers or consult a handy chart, opposite. 

For example: To find the AR of a 5 mm ID, 16-gauge jump ring, first convert to inches:

5 mm ID = (5 x.0394) = 0.197 in. 

16-gauge wire = 0.051 in.

Plug these numbers into the basic formula: ID ÷ gauge = AR:

0.197 ÷ 0.051 = 3.86

The AR of a 5 mm ID, 16-gauge jump ring is 3.86. 


Many chain mail patterns require a basic understanding of AR. One of the most well known is the Jens Pind. When making a Jens Pind chain, like the one above, I use 6 mm ID, 12-gauge jump rings. So:

0.236 ÷ 0.081 = 2.91 AR

This is a tight AR. Each link has to hold three rings snugly with a minimum of movement. If the rings are too loose, won’t hold. If the rings are too small,the pattern will be too stiff, if it works at all.

Use this PDF chart as a reference with samples of chain to illustrate a variety of ARs along with a handy gauge inches to millimeters chart

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