Conversion chart

Ring size chart for every country.

Every value below is calculated from the published standard for that country at build time — the US trade scale, ISO 8653, the British Wheatsheaf letters, JIS S 4700 and NBR 16058. Nothing here was copied from another chart, which is how charts pick up errors.

Measure my size What the numbers mean

The full chart

Rows step in half US sizes. Inside diameter is the measurement across the opening; circumference is the distance around it. Scroll sideways to see every region.

Scroll the table sideways to see every region

Ring size conversion across all national standards, with inside diameter and circumference in millimetres
Diameter	Circum.	US / CA	UK / AU	EU / ISO	France	DE / NL	Russia	IT / ES / CH	Brazil	Japan	China / HK	India
14.07 mm	44.2 mm	3	F½	44	44	14	14	4	4	4	4	4
14.47 mm	45.5 mm	3½	G½	45.5	45.5	14.5	14.5	5.5	5.5	5	5	5
14.88 mm	46.8 mm	4	H½	47	47	15	15	7	7	7	7	7
15.29 mm	48.0 mm	4½	I½	48	48	15.5	15.5	8	8	8	8	8
15.69 mm	49.3 mm	5	J½	49.5	49.5	15.5	15.5	9.5	9.5	9	9	9
16.10 mm	50.6 mm	5½	K½	50.5	50.5	16	16	10.5	10.5	10	10	10
16.51 mm	51.9 mm	6	L½	52	52	16.5	16.5	12	12	12	12	12
16.91 mm	53.1 mm	6½	M½	53	53	17	17	13	13	13	13	13
17.32 mm	54.4 mm	7	N½	54.5	54.5	17.5	17.5	14.5	14.5	14	14	14
17.73 mm	55.7 mm	7½	O½	55.5	55.5	17.5	17.5	15.5	15.5	15	15	15
18.13 mm	57.0 mm	8	P½	57	57	18	18	17	17	16	16	16
18.54 mm	58.2 mm	8½	Q½	58	58	18.5	18.5	18	18	18	18	18
18.95 mm	59.5 mm	9	R½	59.5	59.5	19	19	19.5	19.5	19	19	19
19.35 mm	60.8 mm	9½	S½	61	61	19.5	19.5	21	21	20	20	20
19.76 mm	62.1 mm	10	T½	62	62	20	20	22	22	21	21	21
20.16 mm	63.3 mm	10½	U½	63.5	63.5	20	20	23.5	23.5	22	22	22
20.57 mm	64.6 mm	11	V½	64.5	64.5	20.5	20.5	24.5	24.5	24	24	24
20.98 mm	65.9 mm	11½	W½	66	66	21	21	26	26	25	25	25
21.38 mm	67.2 mm	12	X½	67	67	21.5	21.5	27	27	26	26	26
21.79 mm	68.5 mm	12½	Z	68.5	68.5	22	22	28.5	28.5	27	27	27
22.20 mm	69.7 mm	13	Z+1	69.5	69.5	22	22	29.5	29.5	29	29	29
22.60 mm	71.0 mm	13½	Z+2	71	71	22.5	22.5	31	31	30	30	30

Sizes are rounded to the granularity each country actually sells. Where a country sells only whole numbers, the nearest whole size is shown — ask for the millimetre value if you fall between two.

What each number actually means

A “size 12” means five different things in five different countries. Here is the definition behind every column above.

United States & Canada

US / CA

Proprietary numeric scale: diameter = 0.8128 × size + 11.63 mm

Used in: United States, Canada, Mexico

UK, Ireland, Australia, NZ & South Africa

UK / AU

Wheatsheaf letters: size C = 40 mm circumference, 1.25 mm per letter

Used in: United Kingdom, Ireland, Australia, New Zealand, South Africa

ISO 8653 (European)

EU / ISO

Size = inside circumference in millimetres

Used in: Austria, Belgium, Germany, Denmark, Finland, Norway, Sweden, Poland, Portugal

ISO 8653:2016 tabulates 41–76 mm with a ±0.02 mm tolerance.

France

Size = inside circumference in millimetres

Used in: France

French retailers usually quote the full ISO circumference (e.g. taille 52). A minority still use the older “circumference − 40” form — that value is the Italy/Spain/Switzerland column. Check which one your jeweller means.

Germany & Netherlands

DE / NL

Size = inside diameter in millimetres

Used in: Germany, Netherlands

Russia & Ukraine

Russia

Size = inside diameter in millimetres, to the nearest half

Used in: Russia, Ukraine, Belarus

Italy, Spain & Switzerland

IT / ES / CH

Size = inside circumference in millimetres, minus 40

Used in: Italy, Spain, Switzerland

Brazil

NBR 16058: size = (diameter × π) − 40

Used in: Brazil

This is the current NBR 16058:2012 scale. Older Brazilian charts use a different, incompatible numbering — confirm before ordering vintage stock.

Japan (JIS S 4700)

Japan

JIS 号数: size 1 = 13 mm diameter, ⅓ mm per size

Used in: Japan, South Korea

China & Hong Kong

China / HK

Integer scale equivalent to the Japanese 号数 scale

Used in: China, Hong Kong, Taiwan

China has no national ring standard. Most jewellers use the Japanese-equivalent number shown here (港號), but some quote the ISO circumference instead. Send your jeweller the millimetre measurement to be certain.

India

Integer scale equivalent to the Japanese 号数 scale

Used in: India, Sri Lanka, Nepal

Indian jewellers broadly follow the Japanese-equivalent numbering, but workshop scales vary regionally. Quote the millimetre diameter alongside the number.

How to read a conversion

Ring sizes are not interchangeable across countries because the underlying scales are not the same shape. The US scale steps by exactly 0.8128 mm of inside diameter per whole size — one thirty-second of an inch. The British letters step by 1.25 mm of circumference, which works out to about half a US size per letter. ISO sizes simply are the circumference in millimetres.

Because the steps differ, a whole size in one system rarely lands on a whole size in another. That is why a US 6 is a British L½ rather than a round letter, and why any chart that shows only whole numbers is hiding a rounding decision from you.

If you are ordering across borders, the safest thing you can send a jeweller is not a size at all — it is the inside diameter in millimetres. Every workshop in the world can work from that, and it survives translation between every system above.

Measure to the millimetre

Ring size charts by country

Each page explains how that country writes a ring size, what it measures in millimetres, and how it converts to every other system.