Reference

International ring size chart

US 3 to 13.5 in half-size steps, with every system on one row. Diameter and circumference are the physical measurements; the other columns are labels for them — and three of those labels are approximate, on purpose.

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International ring size chart: US, UK, Australia, EU and India equivalents with inner diameter and circumference.
US / Canada	UK (approx.)	Australia (approx.)	EU / ISO	India (approx.)	Inner diameter	Inner circumference
3	F	F	44	4	14.07 mm	44.2 mm
3.5	G	G	46	6	14.48 mm	45.5 mm
4	H	H	47	7	14.88 mm	46.7 mm
4.5	I	I	48	8	15.29 mm	48.0 mm
5	J	J	49	9	15.70 mm	49.3 mm
5.5	K	K	51	11	16.10 mm	50.6 mm
6	L	L	52	12	16.51 mm	51.9 mm
6.5	M	M	53	13	16.92 mm	53.2 mm
7	N	N	54	14	17.32 mm	54.4 mm
7.5	O	O	56	16	17.73 mm	55.7 mm
8	P	P	57	17	18.14 mm	57.0 mm
8.5	Q	Q	58	18	18.54 mm	58.2 mm
9	R	R	60	20	18.95 mm	59.5 mm
9.5	S	S	61	21	19.35 mm	60.8 mm
10	T	T	62	22	19.76 mm	62.1 mm
10.5	U	U	63	23	20.17 mm	63.4 mm
11	V	V	65	25	20.57 mm	64.6 mm
11.5	W	W	66	26	20.98 mm	65.9 mm
12	X	X	67	27	21.39 mm	67.2 mm
12.5	Y	Y	69	29	21.79 mm	68.5 mm
13	Z	Z	70	30	22.20 mm	69.7 mm
13.5	Z+1	Z+1	71	31	22.61 mm	71.0 mm

UK, Australia and India columns are labelled approximate because published charts disagree (see the country pages and the sources report). EU is the ISO circumference, rounded to a whole millimetre. Diameter and circumference are the physical measurements every other column is read from.

Note: UK, Australia and India columns are labelled approximate because published charts disagree: UK by a half-letter in places, Australia by up to about 0.3 mm for the same letter, India by ±1 size at some rows. EU is different: it is the ISO circumference, rounded to a whole millimetre, so it is exact within that rounding. When a seller's chart and this chart disagree, trust the millimetre diameter and circumference, not the label.

Related guides

Ring size converter
Convert one system to another, with rounding notes and unavailable handling.
US ring size chart
The US / Canada system on its own: numbers, half sizes, and examples.
UK ring size chart
The UK letter system on its own, including why charts disagree.
EU ring size chart
ISO 8653: the circumference system, 44 to 72.
India ring size chart
The Indian number system and its circumference − 40 rule.
International ring sizes
All systems compared, plus the ones deliberately not shipped as definitive.