Math and Jewelry

8 09 2010

When you make a ring, it’s always a little tricky figuring out how much material you need. For some techniques, such as wire wrapping, or riveting, it’s easy… and you can always make small adjustments. But when you’re making a soldered band, you need to know how long the strip should be.

I will be teaching a rings class in a few weeks that requires being able to figure this out… that’s where math comes in!

A Perfect Fit... Message Rings

I love these rings… but then again, I love stamping and heavy metal!! It can be tempting to buy a prefabricated band and just stamp a pattern or message on them, but it is too easy to stretch the ring a bit when stamping. If you create the pattern on flat stock, then cut it to appropriate length and solder, you are guaranteed a good fit. And this is really really important when making a custom ring!

The length of the stock metal sheet will vary, depending on how thick the metal is. A ring made with thicker gauge metal needs to be longer than one made with thinner gauge to accommodate for the matching of the cut ends. So what is the magic formula used??

(diameter x pi) + (thickness x pi) = metal length

You remember “pi” don’t you…. from high school?? Well, we will only need to use pi two places out to 3.14. It is much much, much easier to use millimeters (mm) instead of inches, since mm are smaller, so the sizing is more exact. So here is an example using 18g metal (1.02mm) in a size 7 ring (17.35mm diameter):

(17.35 x 3.14) + (1.02 x 3.14) = 54.48 + 3.20 = 57.68mm length

Really, the formula is easy, and it’s not difficult to do – just cut metal a little longer (ie: 59mm) to get started, and stamp your design across the band. Re-measure and mark the metal to be as close as possible to 58mm (I always round up), then cut. file and sand the edges flush, so that when they meet, they do not have a gap. Fold the metal ends gently together, then solder and finish off as usual.

Formula Works for All Band Styles!

For this ring, a strip of silver was soldered to one end of the copper disc. The overall length was determined using the formula above, and then the measurement was marked on the metal, including the radius of the disc into the length – easy!!

Or, if you prefer… you can always download a table online with the sizing already figured out!



6 responses

11 09 2010
Studio MME

Wow, I had no idea so much math was involved. I think I’ll stick to just buying jewelry and let you metalsmithing artists do the math for me. 🙂

11 09 2010

Most folks just use a chart (much easier!)!

6 10 2010

Hope this isn’t too stupid, but what does the added 3.20 at the end of your equation represent?

6 10 2010

Hi AJ… In the formula, the metal thickness x pi is 3.20mm:
Diameter(pi)= (17.35 x 3.14) = 54.48
Thickness(pi) = (1.02 x 3.14) = 3.20
Length = 54.48 + 3.20 = 57.68mm

Hope that makes sense…. I use a chart, but it’s good to know the “how” behind the numbers!

6 10 2010

DUH!! I just wasn’t reading it correctly. Guess I have been away from Algebra for way too long! Thanks for clearing it up.

7 04 2012
Smokey Quartz Pendant

Thank you for sharing the information about rings. One of these days I’m going to try making making rings – I do them now using wire wrapping, but haven’ttried metal work yet. Soon . . . and your tip will be very helpful.


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