Ring size converter.

How to measure your ring size at home

No ring sizer handy? A strip of paper or a piece of string does the job:

1. Wrap a thin strip of paper or a piece of non-stretchy string snugly around the base of your finger — not too tight, not loose enough to slide off over the knuckle.
2. Mark the point where the two ends meet (or overlap) with a pen.
3. Lay the strip flat and measure the length from the start to your mark with a ruler, in millimetres. That's your circumference.
4. Enter that number as circumference (mm) below, or divide it by π (about 3.14159) to get the diameter and enter that instead.

Measure at the end of the day when fingers are largest, avoid measuring when you're cold (fingers shrink), and if you're between sizes, size up rather than down — a slightly loose ring is more comfortable than one that won't come off.

About ring size conversion

US/Canada ring sizes are a numeric scale where each whole size is a fixed step in circumference; UK/Australia sizes use a letter scale (A through Z) with roughly one letter per half a US size. This converter uses the standard ISO-referenced circumference and diameter values for each size, so a US 7 (UK/AU N) corresponds to an internal circumference of about 54.4 mm and a diameter of about 17.3 mm.