Ring Size Converter (International)

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How to Use this Ring Size Converter

The calculator is quite easy to use, here is what you need to do:

Specify the ring size standard you want to convert from
Select the original ring size
Specify the target ring standard
Press the ‘Calculate’ button to get the new size

Please keep in mind that the calculation result will be ‘NA’ if there is no equivalent ring size available in the target standard.

In case you’re not sure about your ring size, you may use a ring sizer.

The Included Ring Size Standards

The calculator will allow you to convert between the ring sizes for Europe (ISO), US, UK, Japan, Swiss and Russia.

We also added the option to use the inside circumference/diameter of ring in millimeters or inches if it’s needed.

In case you wonder where in the world each standard is used, here is a summary:

Ring Size Standard	Countries
ISO (Europe)	Austria, France, Belgium, Scandinavia, Norway, Sweden, Denmark, Finland, Iceland and other countries in Continental Europe
North American (US)	US, Canada and Mexico
British (UK)	UK, Ireland, Australia, New Zealand and South Africa
East Asia (Japan)	Japan, India, China and South Korea
Swiss (Switzerland)	Italy, Spain and Switzerland
German (Russia)	Germany, Netherlands, Russia and Argentina

How the Ring Size Converter Works

The calculator here uses ring size chart for converting the ring size for all standards with a slight modification (rounding).

The only exception to the above is the Russia standard. Here, the ring size is simply the inside diameter in millimeters rounded to the nearest quarter (starting from 13).

Here is the full size chart:

Ring Size						Inside Diameter		Inside Circumference
Europe (ISO)	US	UK	Japan	Switzerland	Russia	(mm)	(in)	(mm)	(in)
36.5	0	–	–	–	–	11.63	0.458	36.5	1.44
37	1⁄4	–	–	–	–	11.84	0.466	37.14	1.46
38	1⁄2	A	–	–	–	12.04	0.474	37.78	1.49
38.5	3⁄4	A 1⁄2	–	–	–	12.24	0.482	38.41	1.51
39	1	B	1	–	–	12.45	0.49	39.05	1.54
39.5	1 1⁄4	B 1⁄2	–	–	–	12.65	0.498	39.69	1.56
40.5	1 1⁄2	C	–	–	–	12.85	0.506	40.33	1.59
41	1 3⁄4	C 1⁄2	–	1	13	13.06	0.514	40.96	1.61
41.5	2	D	2	1 1⁄2	13 1⁄4	13.26	0.522	41.6	1.64
42	2 1⁄4	D 1⁄2	–	2 1⁄4	13 1⁄2	13.46	0.53	42.24	1.66
43	2 1⁄2	E	3	3	13 3⁄4	13.67	0.538	42.88	1.69
43.5	2 3⁄4	E 1⁄2	–	3 1⁄2	–	13.87	0.546	43.51	1.71
44	3	F	4	4 1⁄4	14	14.07	0.554	44.15	1.74
45	3 1⁄4	F 1⁄2	5	4 3⁄4	14 1⁄4	14.27	0.562	44.79	1.76
45.5	3 1⁄2	G	–	5 1⁄2	14 1⁄2	14.48	0.57	45.43	1.79
46	3 3⁄4	G 1⁄2	6	6	14 3⁄4	14.68	0.578	46.06	1.81
46.5	4	H	7	6 3⁄4	–	14.88	0.586	46.7	1.84
47.5	4 1⁄4	H 1⁄2	–	7 1⁄4	15	15.09	0.594	47.34	1.86
48	4 1⁄2	I	8	8	15 1⁄4	15.29	0.602	47.98	1.89
48.5	4 3⁄4	J	–	8 1⁄2	15 1⁄2	15.49	0.61	48.61	1.91
49.5	5	J 1⁄2	9	9 1⁄4	15 3⁄4	15.7	0.618	49.25	1.94
50	5 1⁄4	K	–	10	–	15.9	0.626	49.89	1.96
50.5	5 1⁄2	K 1⁄2	10	10 1⁄2	16	16.1	0.634	50.53	1.99
51	5 3⁄4	L	–	11 1⁄4	16 1⁄4	16.31	0.642	51.16	2.01
52	6	L 1⁄2	11	11 3⁄4	16 1⁄2	16.51	0.65	51.8	2.04
52.5	6 1⁄4	M	12	12 1⁄2	16 3⁄4	16.71	0.658	52.44	2.06
53	6 1⁄2	M 1⁄2	13	13	17	16.92	0.666	53.08	2.09
53.5	6 3⁄4	N	–	13 3⁄4	–	17.12	0.674	53.71	2.11
54.5	7	N 1⁄2	14	14 1⁄4	17 1⁄4	17.32	0.682	54.35	2.14
55	7 1⁄4	O	–	15	17 1⁄2	17.53	0.69	54.99	2.16
55.5	7 1⁄2	O 1⁄2	15	15 3⁄4	17 3⁄4	17.73	0.698	55.63	2.19
56.5	7 3⁄4	P	–	16 1⁄4	18	17.93	0.706	56.26	2.22
57	8	P 1⁄2	16	17	–	18.14	0.714	56.9	2.24
57.5	8 1⁄4	P 3⁄4	–	17 1⁄2	18 1⁄4	18.34	0.722	57.54	2.27
58	8 1⁄2	Q 1⁄4	17	18 1⁄4	18 1⁄2	18.54	0.73	58.18	2.29
59	8 3⁄4	R	–	18 3⁄4	18 3⁄4	18.75	0.738	58.81	2.32
59.5	9	R 1⁄2	18	19 1⁄2	19	18.95	0.746	59.45	2.34
60	9 1⁄4	S	–	20	19 1⁄4	19.15	0.754	60.09	2.37
60.5	9 1⁄2	S 1⁄2	19	20 3⁄4	–	19.35	0.762	60.73	2.39
61.5	9 3⁄4	T	–	21 1⁄4	19 1⁄2	19.56	0.77	61.36	2.42
62	10	T 1⁄2	20	22	19 3⁄4	19.76	0.778	62	2.44
62.5	10 1⁄4	U	21	22 3⁄4	20	19.96	0.786	62.64	2.47
63.5	10 1⁄2	U 1⁄2	22	23 1⁄4	20 1⁄4	20.17	0.794	63.28	2.49
64	10 3⁄4	V	–	24	–	20.37	0.802	63.91	2.52
64.5	11	V 1⁄2	23	24 1⁄2	20 1⁄2	20.57	0.81	64.55	2.54
65	11 1⁄4	W	–	25 1⁄4	20 3⁄4	20.78	0.818	65.19	2.57
66	11 1⁄2	W 1⁄2	24	25 3⁄4	21	20.98	0.826	65.83	2.59
66.5	11 3⁄4	X	–	26 1⁄2	21 1⁄4	21.18	0.834	66.46	2.62
67	12	X 1⁄2	25	27	–	21.39	0.842	67.1	2.64
67.5	12 1⁄4	Y	–	27 3⁄4	21 1⁄2	21.59	0.85	67.74	2.67
68.5	12 1⁄2	Y 1⁄2	26	28 1⁄2	21 3⁄4	21.79	0.858	68.38	2.69
69	12 3⁄4	Z	–	29	22	22	0.866	69.01	2.72
69.5	13	Z+1⁄2	27	29 3⁄4	22 1⁄4	22.2	0.874	69.65	2.74
70.5	13 1⁄4	Z+1	–	30 1⁄4	22 1⁄2	22.4	0.882	70.29	2.77
71	13 1⁄2	Z+1.5	–	31	–	22.61	0.89	70.93	2.79
71.5	13 3⁄4	Z+2	–	31 1⁄2	22 3⁄4	22.81	0.898	71.56	2.82
72	14	Z+3	–	32 1⁄4	23	23.01	0.906	72.2	2.84
73	14 1⁄4	Z+3.5	–	32 3⁄4	23 1⁄4	23.22	0.914	72.84	2.87
73.5	14 1⁄2	Z+4	–	33 1⁄2	23 1⁄2	23.42	0.922	73.48	2.89
74	14 3⁄4	Z+4.5	–	34	–	23.62	0.93	74.11	2.92
75	15	Z+5	–	34 3⁄4	23 3⁄4	23.83	0.938	74.75	2.94
75.5	15 1⁄4	Z+5.5	–	35 1⁄2	24	24.03	0.946	75.39	2.97
76	15 1⁄2	Z+6	–	36	24 1⁄4	24.23	0.954	76.03	2.99
76.5	15 3⁄4	Z+6.5	–	36 3⁄4	24 1⁄2	24.43	0.962	76.66	3.02
77.5	16	Z+7	–	37 1⁄4	24 3⁄4	24.64	0.97	77.3	3.04

Please note the ring size for ISO is just the inner circumference of ring in millimeters rounded to half.

Conclusion

We hope the above ring size converter was helpful for buying your next beautiful ring, whether for yourself or for your significant other.

To use this online tool; just pick the ring size system to convert from and the one to convert to along with the size value, then the calculator will do the rest.

Feel free to let us know if you find anything in the tool that’s inaccurate so we can correct it. Also, we would love to hear any suggestions or questions about it.

FAQ

Does 1/2 ring size make a difference?

A half ring size in US standard can make a difference. It can add or subtract a little over one millimeter from the inside circumference of ring.

How to convert cm to ring size?

To get the ring size in international standard (ISO), convert the circumference from centimeters to millimeters then round to the nearest half. For the US ring size; subtract 36.5 from the circumference in millimeters, divide by 2.55, then round to the nearest quarter.

How do I convert my US ring size to UK?

To convert a US ring size to UK size, simply divide it by half to get the letter number. For example, a US size of three divided by half is six (which indicates a UK size of ‘F’). If the result includes a half rather than an integer, then include a half fraction after the letter such as C 1/2 for US size 1 3/4.

Are ring sizes universal?

While there is an international standard for ring sizes (ISO), there are other systems utilized in different regions such as the British (UK and Australia) and Swiss (Switzerland and Italy).

What is the smallest ring size?

The smallest ring size is 36.5 ISO or zero in US standard.

How to Use this Ring Size Converter

The Included Ring Size Standards

How the Ring Size Converter Works

Conclusion

FAQ

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