Last updated: 4/26/22, 3/3/17
Nancy LT Hamilton
Calculating ring blank size based on interior dimensions
See my page Inside Ring Blank Measurement. Find your ring size and its interior dimensions or vice versa.
The formula for ID blank sizing
To figure out your own sizing (instead of using the chart) here’s the formula: (ID + metal thickness) X pi = ring blank length. Pi is (3.14159265359+). Some round Pi up to 3.15, or even 3.5 to take into account edge cleanup and other fun things. Try this first with scrap to see what version of Pi you need to use. A lot depends on your skills, your tools, and which way the wind is blowing! Haha.
Add .5mm if the metal used is over 4mm wide.
Need to find out what your gauge is in millimeters or inches?
See my B&S Gauge Chart
How much metal you remove from the ends, how you mark the metal, and how cleanly you cut the metal are all contributing factors to whether we create just the right size, need to stretch our blank, or even find a need to shrink it. Experimentation is the way to go. Keep a notebook of what works. Try to be consistent.
Getting a perfectly sized ring is an iffy proposition but, not impossible. Our ring sizes change throughout the day, month and year – not to mention over a lifetime – some more than others. Hot weather can increase ring sizes as can water retention, arthritis, medication, salt, alcohol, exercise, etc. So, at any two points in a day, we can have varying ring sizes.
If possible, have your customer measure their finger size over time and under different conditions: during exercise, before and after taking medication, before and after that bag of chips! This should give you an average to work with.
Want to skip the math and are too tired to look at the chart? Here’s a Ring Blank Calculator by Mordent Design.
Related Web Pages
- Adjustable Ring Size Chart
- Links: Books page for other great jewelry-making books.
- Ring Size Conversion Chart – Convert your ring size to the ring size used in other countries.
- Q&A: Rings
- Ring Blank Chart
- Ring, Bracelet, and Bezel Mandrels
- Saddle Ring Pattern
- Stones and Stone Setting
- Texturing Metal
Related Reference Books