Ring Size Calculator
Find your US and UK ring size from a diameter or circumference measurement in millimeters.
Last updated: September 23, 2026
Ring Size Chart (US to UK Conversion)
This chart shows standard ring sizes from US 3 to US 13, with the matching UK/Australia size and the exact inside diameter and circumference in millimeters.
| US Size | UK / AU Size | Diameter (mm) | Circumference (mm) |
|---|
How to measure your ring size at home
Wrap a thin strip of paper or string snugly around the base of the finger you'll wear the ring on, mark where the ends meet, then lay it flat and measure the length in millimeters that's your circumference. You can also measure the inside diameter of a ring that already fits well. If you're also looking to find your correct clothing size, try our free bra size calculator which uses similar measurement techniques with band and bust measurements.
FAQ
Is this chart accurate for all ring styles?
This chart reflects standard sizing. Wide bands typically fit more snugly, so many jewelers recommend going up half a size for wider styles.
Why do US and UK ring sizes use different scales?
The US system uses numbers (3-13+), while the UK, Ireland, Australia, and South Africa use letters (A-Z and beyond) both map to the same underlying millimeter measurements, which is what this calculator converts between.