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International ring size converter

Pick a size in one system and see it in all the others.

From

Size

US–

UK–

EU–

Japan–

Reference table

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US	UK	EU (ISO)	Japan	Diameter mm	Circumference mm
3	F	44	4	14.1	44.2
3½	G	45	—	14.5	45.5
4	H	47	7	14.9	46.8
4½	I	48	8	15.3	48.0
5	J½	49	9	15.7	49.3
5½	K½	51	10	16.1	50.6
6	L½	52	11	16.5	51.9
6½	M½	53	13	16.9	53.1
7	N½	54	14	17.3	54.4
7½	O½	56	15	17.7	55.7
8	P½	57	16	18.1	57.0
8½	Q¼	58	17	18.5	58.2
9	R½	60	18	18.9	59.5
9½	S½	61	19	19.4	60.8
10	T½	62	20	19.8	62.1
10½	U½	63	22	20.2	63.3
11	V½	65	23	20.6	64.6
11½	W½	66	24	21.0	65.9
12	X½	67	25	21.4	67.2
12½	Y½	68	26	21.8	68.5
13	Z½ (approx.)	70	27	22.2	69.7

“Women” shows US 3–9 and “Men” US 8–13. These are just filters to shorten the table; anyone can wear any size. Japan: “—” means there is no matching Japanese size.

Sources

How we calculate: the EU size is the inner circumference in millimetres, as defined in ISO 8653:2016. US sizes follow the US scale where each whole size adds 0.032 in (0.8128 mm) to the inner diameter, so diameter = 11.63 mm + 0.8128 mm × US size. UK letters follow British Standard 6820:1987 (size C = 40 mm circumference, each letter adds 1.25 mm). Japanese sizes come from the equivalency table on Wikipedia (Japanese sizes are whole numbers that do not follow a straight formula, so they are rounded to the nearest size). Sources: ISO 8653:2016, Ring size (Wikipedia), equivalency table, Larson Jewelers conversion chart. Charts from different jewelers can round slightly differently, so for an important ring check with the jeweler.

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Calibrate with a bank card, lay a ring on the screen and read the size in four systems.

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