Professional Ring Blank Sizing Chart and Calculator

This article provides a calculator (and the formula behind it) to help you find the correct length ring blank to ensure you finish with the desired ring size.

Last edited: 10/29/2020
Jeweler at bench sitting a ring blank

Measuring for a Ring Blank

To get a proper ring fit, you must compensate for the thickness of the ring band before you measure the blank. Curving the outside ends of the blank together for soldering compresses the inside circumference, making the ring smaller. To correct for this, the calculator instantly computes the additional length necessary to allow for the compression, allowing your finished ring to reliably finish at the size you want. Important: Ring sizers and ring sticks are generally not calibrated to one another or from brand to brand across the wide array of available options; their measurements will vary slightly, as will the charts you find online and in books. Be aware of this as you compare one to another—the measurements usually are only very slightly off, but they will be off.

Ring and sizing graphic for determining the measurements of a ring blank

Ring Blank Size Calculator

Enter your desired ring size dimensions below to instantly calculate the proper size ring blank you need to cut.

Desired Ring Size:
Metal Thickness:
Ring Width:

Your ring blank length: mm

Want to Know How It Works?

If you're interested to see how to apply to formula by hand, the formula used is shown below.

[inner diameter + metal thickness] x 3.1416 (pi) = correct blank length (add an additional 0.5mm if over 4mm wide)

Take the inner diameter, add the metal thickness and multiply by pi (3.1416). Add the resulting number to the inner circumference of your desired ring size. This gives you the necessary length for your ring blank length. If the ring band is wider than 4mm, add an extra 0.5mm to ensure an excellent fit.

The chart below gives you the inside circumference measurements of a variety of ring sizes:

US Ring Size / Inside Circumference / Inside Diameter Conversion Chart
Ring Size 1 2 3 4 5 6 7
IC mm 38.86 40.15 41.50 42.76 44.14 45.40 46.68 47.94 49.36 50.60 51.87 53.16 54.51 55.76
ID mm 12.37 12.78 13.21 13.61 14.05 14.45 14.90 15.26 15.70 16.10 16.51 16.92 17.35 17.75

Ring Size 8 9 10 10½ 11 11½ 12 12½ 13 13½ 14 14½
IC mm 57.15 58.40 59.69 60.98 62.27 63.59 64.97 66.22 67.51 68.46 69.74 71.03 72.29 73.58
ID mm 18.19 18.59 19.00 19.41 19.82 20.24 20.68 21.08 21.49 21.79 22.22 22.61 23.01 23.42