Every ring size is defined by the inside diameter/circumference of the band. The calculator compares your measurement to the standard size table and returns the nearest match in each country's system. If your measurement falls between two sizes, it suggests rounding up.
Tips for accuracy
Measure at the end of the day; fingers swell and are largest then.
Don't measure cold hands.
Size up half a size for wide bands.
Make sure the size clears your knuckle.
Note: results are approximate and rounded to standard sizes. For a valuable or made-to-order ring, confirm with a jeweler.
Enter the inside diameter or circumference of your finger (or a ring that fits) in millimetres, and the calculator matches it to the closest standard size in US, UK, Europe, Japan and India.
How do I measure my finger in millimetres?
Wrap a strip of paper or string around the base of your finger, mark where it overlaps, then measure that length with a ruler in millimetres — that's your circumference. Or measure the inside diameter of a ring that already fits.
Which is more accurate, diameter or circumference?
Both work. Circumference (the string method) is usually easiest to measure at home; diameter is easiest if you already have a ring that fits.
Should I size up for a wide band?
Yes. Wide bands (6 mm or more) fit more snugly, so it's common to go up about half a size.
Does this calculator store my data?
No. The calculation runs entirely in your browser — nothing is uploaded or saved.