Size Chart - Rings

US UK EU INSIDE DIAMETER (MM) CIRCUMFERENCE (MM)
5 J ½ 49 15.7 49.3
6 L ½ 51.5 16.5 51.9
7 N ½ 54 17.3 54.4
8 P ½ 57 18.2 57.0
9 R ½ 59.5 19.0 59.5
10 T ½ 61.5 19.8 62.1

It fits true to size — if you're between sizes or prefer a little more ease, consider sizing up for an even more relaxed fit.