Ring size · Free tool

Ring size chart and converter.

Every country labels the same ring differently. Underneath, there is only one number that matters: the inner circumference in millimetres. Measure that once and every system falls out of it.

Measuring at home

Wrap a strip of paper around the base of the finger — not thread, which stretches. Mark where it overlaps.
Measure the marked length in millimetres. That is the circumference, and it is the only measurement you need.
Read it off the table below. Find your circumference in the first column; your size in every system is on that row.

Measure in the evening. Fingers are smallest in the morning and swell through the day, and in heat. A ring fitted at 7am will feel tight by dinner.

Check the knuckle. If the knuckle is much wider than the base, size up so the ring passes over it — then have the jeweller fit it.

Wide bands run tighter. Anything over about 6mm wide needs roughly half a size up compared with a thin band.

A jeweller's own chart wins. Makers differ by a fraction of a size, and a proper mandrel beats a paper strip. Use this to know roughly where you are.

The coin trick

Worth being straight about how this one actually works. You cannot slide a ring over a coin to size it — a ₹1 coin is about 22mm across and a typical engagement ring is 15 to 18mm inside, so it will not go on. What a coin is genuinely good for is the thing every printable ring sizer gets wrong.

Printers default to fit to page and quietly shrink the sheet by a few percent. That is enough to throw the reading out by a size or two, and nothing on the page tells you it happened. So put an object of known size on the sheet and check before you trust it. A ₹1 coin is 21.93mm. A bank card is 85.60mm on its long edge — ISO/IEC 7810, identical worldwide.

Printable ring sizer

Print at 100% scale — turn off “fit to page” or “shrink to fit”. Then check the calibration below before you trust the circles.

1. Check the print scale

Lay a coin on its circle, or a bank card along the line. If they match, the sheet printed at true size. If they are off, reprint at 100%.

2. Lay a ring she already wears over the circles

The right one is where the circle's edge just disappears under the inside of the band. Use a ring worn on the same finger — hands differ.

US size shown large · Indian and UK equivalents beneath · loveontales.com

If it's meant to be a surprise

The hard case: you need her size without asking. In rough order of how well they work.

Borrow a ring she already wears on that finger and press it into a bar of soap or a lump of clay. Measure the impression, or lay the ring on the printed circles above. This is by far the most accurate.
Trace the inside on paper. Less exact than an impression but it takes ten seconds and the ring goes straight back.
Ask her sister or closest friend. They often already know, and they can ask casually in a way you cannot.
If you have to guess, guess up. The average woman's ring finger in India is around a size 12 to 14 Indian (US 6 to 7). Most metals resize down more easily than up, and a ring that will not go on ruins the moment in a way a loose one does not.

Do not measure her hand while she sleeps. It is in every listicle, it wakes people, and a relaxed sleeping hand measures smaller than a waking one anyway.

Thread and string lie. Both stretch as you pull them, which is why the paper strip method exists.

Every system, side by side

Circumference	Diameter	Indian	US / Canada	EU / ISO 8653	UK / Australia	Japan / China	Swiss
44 mm	14.01 mm	3	3	44	F½	4	4
45 mm	14.32 mm	5	3½	45	G	6	5
46 mm	14.64 mm	6	3½	46	H	7	6
47 mm	14.96 mm	7	4	47	H½	8	7
48 mm	15.28 mm	8	4½	48	I½	9	8
49 mm	15.60 mm	9	5	49	J½	10	9
50 mm	15.92 mm	10	5½	50	K	11	10
51 mm	16.23 mm	11	5½	51	L	12	11
52 mm	16.55 mm	13	6	52	L½	13	12
53 mm	16.87 mm	14	6½	53	M½	14	13
54 mm	17.19 mm	15	7	54	N	15	14
55 mm	17.51 mm	16	7½	55	O	16	15
56 mm	17.83 mm	17	7½	56	P	18	16
57 mm	18.14 mm	18	8	57	P½	19	17
58 mm	18.46 mm	19	8½	58	Q½	20	18
59 mm	18.78 mm	20	9	59	R	21	19
60 mm	19.10 mm	22	9	60	S	22	20
61 mm	19.42 mm	23	9½	61	S½	23	21
62 mm	19.74 mm	24	10	62	T½	24	22
63 mm	20.05 mm	25	10½	63	U½	25	23
64 mm	20.37 mm	26	11	64	V	26	24
65 mm	20.69 mm	27	11	65	W	27	25
66 mm	21.01 mm	28	11½	66	W½	—	26
67 mm	21.33 mm	29	12	67	X½	—	27
68 mm	21.65 mm	—	12½	68	Y	—	—

Charts by country

How these conversions are worked out

Nothing here is a copied table. Circumference is the physical quantity; every system is a formula on top of it, and the diameter is simply circumference ÷ π.

System	Formula
EU / ISO 8653	`size = circumference` — definitional
US / Canada	`circumference = 36.5 + 2.55 × size`
India	`circumference = 40.9 + 0.8875 × size`
Japan / China	`circumference = 39.9 + 0.917 × size`
Switzerland	`circumference = 40 + size`
UK / Australia	letter scale, anchored so US 6 = UK L½

Checked against the standard correspondence US 6 = EU 52 = UK L½ = India 12 = Japan 13 = Swiss 12, all at 51.8 mm circumference and 16.5 mm diameter. If your jeweller's chart says something a fraction different, go with theirs.