Ring Size Calculator

How to Measure a Ring Size at Home

There are two reliable methods, and one that is worth avoiding.

Method 1 — measure a ring that already fits

Lay the ring on a millimetre ruler and measure straight across the inside edge to inside edge. That is the inside diameter. It is the more accurate of the two methods because the ring is a rigid object and does not compress. Choose a ring worn on the same finger of the same hand.

Method 2 — wrap the finger

Cut a strip of paper about 5 mm wide, wrap it snugly around the base of the finger, mark where it overlaps, and measure the length to the mark in millimetres. That length is the circumference. Pull it just tight enough that it will still slide over the knuckle.

Avoid string

String and thread stretch, and they bite into the skin, which is why they typically read half a size small. If string is all you have, measure it three times and take the largest reading.

The Knuckle Rule

A ring has to pass the knuckle, so the knuckle sets the minimum size even when the base of the finger is narrower. If the knuckle is noticeably larger — a difference of more than about half a size — measure both, order for the knuckle, and ask the jeweller to add sizing beads or a small bar inside the band so the ring does not spin.

Ring Size Chart

Inside diameter and circumference are the real measurements; every national sizing system is a label applied on top of them. The European size is simply the inside circumference in millimetres, rounded.

US / Canada	UK / Australia	Europe	Japan / China	Inside diameter	Inside circumference
3	F	44	4	14.1 mm	44.2 mm
3.5	G	46	5	14.5 mm	45.5 mm
4	H½	47	6.5	14.9 mm	46.8 mm
4.5	I½	48	8	15.3 mm	48.0 mm
5	J½	49	9	15.7 mm	49.3 mm
5.5	K½	51	10.5	16.1 mm	50.6 mm
6	L½	52	11.5	16.5 mm	51.9 mm
6.5	M½	53	13	16.9 mm	53.1 mm
7	N½	54	14	17.3 mm	54.4 mm
7.5	O½	56	15	17.7 mm	55.7 mm
8	P½	57	16	18.1 mm	57.0 mm
8.5	Q½	58	17	18.5 mm	58.3 mm
9	R½	60	18	18.9 mm	59.5 mm
9.5	S½	61	19	19.4 mm	60.8 mm
10	T½	62	20	19.8 mm	62.1 mm
10.5	U½	63	22	20.2 mm	63.4 mm
11	V½	65	23	20.6 mm	64.6 mm
11.5	W½	66	24	21.0 mm	65.9 mm
12	X½	67	25	21.4 mm	67.2 mm
12.5	Y	68	26	21.8 mm	68.5 mm
13	Z	70	27	22.2 mm	69.7 mm
13.5	Z+1	71	28	22.6 mm	71.0 mm
14	Z+2	72	29	23.0 mm	72.3 mm

Typical Sizes

These are averages for adults in the United States, useful only as a sanity check on a measurement — never as a substitute for one.

Wearer	Common range	Most common
Women, ring finger	5 to 7	6
Women, thumb or index	7 to 9	8
Men, ring finger	9 to 11	10
Men, thumb or index	11 to 13	12

Things That Move a Size

• Time of day. Fingers are smallest in the morning and largest in the late evening, a swing of up to half a size. Measure mid-afternoon at normal room temperature.
• Temperature. Cold hands can read a full size small. Warm the hands first.
• Band width. A band wider than about 6 mm sits on more of the finger and feels tighter. Go up a quarter to a half size for a wide band.
• Salt, heat, exercise and pregnancy all cause temporary swelling. So does a long flight.
• Which hand. The dominant hand is usually a quarter to a half size larger.

Buying a Surprise Ring

The reliable approach is to borrow a ring the person already wears on the intended finger and measure its inside diameter with this tool. Failing that, press the ring into a bar of soap or a piece of modelling clay and measure the impression. Guessing from a photograph does not work.

If none of that is possible, order the average size for the wearer and expect to have it resized. Most plain bands can be moved two sizes in either direction by a jeweller; eternity bands set with stones all the way round, and rings in tungsten, titanium or ceramic, generally cannot be resized at all.

Frequently Asked Questions

Can I use a printed ring sizer?

Yes, but print it at 100% scale with no page fitting, then check the calibration line against a ruler before using it. A page scaled to 94% will read a full size out.

What if I am between two sizes?

Take the larger one. A slightly loose ring can be tightened with sizing beads; one that will not clear the knuckle cannot be worn at all.

Is a UK size the same as an Australian size?

Yes. The UK, Ireland, Australia, New Zealand and South Africa all use the same alphabetical system.

How tight should a ring feel?

It should slide on with light resistance and require a small deliberate tug to come off over the knuckle. If it falls off when the hand is shaken, or leaves a deep mark after an hour, the size is wrong.