TABLE OF SIZES

Ring size [Poland and most countries in Europe]	Ring size used in England	Ring size used in USA	Internal diameter [mm]	Internal perimeter [mm]
5	G	4	14,00	43,98
6	H	4+	14,33	45,02
7	H	4+	14,67	46,09
8	I	5	15,00	47,12
9	J	5	15,33	48,16
10	K	6-	15,67	49,23
11	L	6	16,00	50,27
12	L	6	16,33	51,30
13	M	6	16,67	52,37
14	N	7	17,00	53,41
15	O	7	17,33	54,44
16	O	7+	17,67	55,51
17	P	8	18,00	56,55
18	Q	8	18,33	57,59
19	R	9	18,67	58,65
20	S	9	19,00	59,69
21	S	9+	19,33	60,73
22	T	10	19,67	61,80
23	U	10	20,00	62,83
24	V	11-	20,33	63,87
25	V	11	20,67	64,94
26	W	11	21,00	65,97
27	X	12	21,33	67,01
28	Y	12	21,67	68,08
29	Z	13-	22,00	69,12
30	Z	13	22,33	70,15
31	Z+	13	22,67	71,22
32	Z+	14	23,00	72,26
33	Z++	14	23,33	73,29

Helpful information

You should add 0,5 to size while ordering wide wedding rings ( over 5 mm).
Take note that finger sizes sometimes do not correspond to body size. Finger sizes also are prone to change with temperature, humidity, time of day, and other factors.
If you hesitate between two sizes – take the larger.
Rings and gauges are hard metal objects that can be measured exactly, but your finger is flesh and bone, thus not round and it cannot be measured with the same degree of accuracy as the ring.
Remember that knuckles are usually larger than finger. A wedding ring should pass tightly through the knuckle. It may be more loose after it.

Due to differences in measuring devices, a discrepancy between ring size up to 0,5 possible.