Ring Size Comparison Chart

Here's our handy ring size comparison chart showing the equivalent ring sizes between US, UK, the inside diameter and inside circumference in millimeters to help you pick the right ring size.

The ISO standard for ring sizes is ISO 8653:2016, which defines standard ring sizes based on the inner circumference of the ring, measured in millimeters.

An easy way to get your ring size is to get a piece of string, wrap it around your finger, measure how long it is, then use the ring size comparison chart below to convert that to a US or UK ring size.

Keep in mind that you need to get the ring past your knuckle, so don't measure too tightly.

Ring Size Comparison Chart

Inside diameter (mm) ISO	Inside circumference (mm) ISO	US	UK
17.32	54.4	7	N½
17.73	55.7	7½	O½
18.14	57	8	P½
18.54	58.3	8½	Q½
18.95	59.5	9	R½
19.35	60.8	9½	S½
19.76	62.1	10	T½
20.17	63.4	10½	U½
20.57	64.6	11	V½
20.98	65.9	11½	W½
21.39	67.2	12	X½
21.79	68.5	12½	Z
22.2	69.7	13
22.61	71	13½