Ring Size Converter

Convert ring sizes between US, UK, EU and Japan, or start from your finger circumference or ring diameter in millimetres.

Ring size chart

Every size in each system, matched by inside circumference.

USUKEUJPDiameter (mm)Circumference (mm)
3 F 44 4 14.1 44.2
3.25 F½ 45 5 14.3 44.8
3.5 G 45 5 14.5 45.5
3.75 G½ 46 6 14.7 46.1
4 H 47 7 14.9 46.8
4.25 H½ 47 7 15.1 47.4
4.5 I 48 8 15.3 48.0
4.75 I½ 49 8 15.5 48.7
5 J 49 9 15.7 49.3
5.25 J½ 50 10 15.9 49.9
5.5 K 51 10 16.1 50.6
5.75 K½ 51 11 16.3 51.2
6 L 52 12 16.5 51.9
6.25 M 52 12 16.7 52.5
6.5 M½ 53 13 16.9 53.1
6.75 N 54 13 17.1 53.8
7 N½ 54 14 17.3 54.4
7.25 O 55 15 17.5 55.0
7.5 O½ 56 15 17.7 55.7
7.75 P 56 16 17.9 56.3
8 P½ 57 16 18.1 57.0
8.25 Q 58 17 18.3 57.6
8.5 Q½ 58 18 18.5 58.2
8.75 R 59 18 18.7 58.9
9 R½ 60 19 18.9 59.5
9.25 S 60 19 19.1 60.2
9.5 S½ 61 20 19.4 60.8
9.75 T 61 21 19.6 61.4
10 T½ 62 21 19.8 62.1
10.25 U 63 22 20.0 62.7
10.5 U½ 63 22 20.2 63.3
10.75 V 64 23 20.4 64.0
11 V½ 65 24 20.6 64.6
11.25 W 65 24 20.8 65.3
11.5 W½ 66 25 21.0 65.9
11.75 X 67 26 21.2 66.5
12 X½ 67 26 21.4 67.2
12.25 Y 68 27 21.6 67.8
12.5 Y½ 68 27 21.8 68.5
12.75 Z 69 28 22.0 69.1
13 Z½ 70 29 22.2 69.7
13.25 Z+1 70 29 22.4 70.4
13.5 Z+1½ 71 30 22.6 71.0

How to measure your ring size

With string or paper: cut a strip about 10 cm long and 5 mm wide. Wrap it snugly around the base of the finger, mark where the end meets the strip, lay it flat and measure to the mark in millimetres. Choose "Finger circumference" in the converter and type that number.

With a ring that already fits: measure straight across the inside of the ring, from one inner edge to the opposite one, in millimetres. Choose "Ring inside diameter" and type that number.

Measure in the evening, when fingers are warm and at their largest, and measure more than once. The knuckle matters too: the ring has to slide over it, so if your knuckle is much bigger than the base of the finger, size for the knuckle and use a ring adjuster.

Why ring sizes need a chart

Ring sizing is a measurement of the inside of the ring, but every country counts it differently: the EU uses the circumference in millimetres, the US counts steps of 0.8128 mm of diameter, the UK uses letters, and Japan counts steps of a third of a millimetre. The relationship between them is fixed, so this converter works from the circumference and rounds to the nearest size in each system. Different jewellers round slightly differently, so one step either way between charts is normal.

Finding your ring size at home: a worked example

Worked example

You wrap a thin strip of paper around the base of your ring finger, mark where it overlaps, and measure the strip against a ruler. It reads 54.4 mm.

In the converter above, choose "Finger circumference (mm)" and type 54.4. You get US 7, UK N½, EU 54 and Japan 14. That's all there is to it. You can now shop in any of the four systems.

Prefer to measure a ring you already own? Measure straight across the inside, edge to edge. If it reads 17.3 mm, choose "Ring inside diameter" and you'll land on the same size, because 17.3 × π is about 54.4.

Six mistakes that give you the wrong size

  1. Measuring when your hands are cold. Fingers shrink in the cold and swell in the heat. Measure in the evening, at normal room temperature.
  2. Using stretchy string. It gives you a number that's too small. Use a strip of paper, or a thread that doesn't stretch, and measure it against a ruler.
  3. Measuring only once. Do it two or three times on different days and take the middle value. One reading can easily be a millimetre out.
  4. Ignoring your knuckle. The ring has to get over it. If your knuckle is bigger than the base of your finger, size for the knuckle and ask about a ring adjuster for the rest.
  5. Forgetting the width of the band. A wide band covers more of your finger and feels tighter than a thin one. If the band is wide (roughly 6 mm or more), many people go up by a quarter to half a size.
  6. Mixing up the systems. A UK N½ is a US 7, but a UK 7 isn't a US 7. UK sizes are letters, US sizes are numbers and EU sizes are the circumference in millimetres. Always check which system the shop uses.
Why this matters

A ring is one of the few things you can't easily try on before buying online. A ring that's one size out is either too tight to wear or likely to slip off. With an engagement ring, an engraved piece or a custom order, a wrong size can cost you weeks.

Buying a ring from overseas

Here's the safest way to do it. Ask the seller for the inside diameter in millimetres, or the inside circumference, rather than only a size label. That's the number you actually measured, so there's nothing to convert wrongly. If the seller only lists sizes, use the converter above and check their chart against ours: jewellers round differently, so one step either way is normal.

Check the return and resizing policy before you pay. Rings made of tungsten, titanium or ceramic usually can't be resized at all, so those are the ones to get right first time. A ring that's slightly too big can often be fixed with a small adjuster. A ring that's too small can't be worn.

Do ring sizes change?

Yes, a little. Heat, salt, a long day on your feet and changes in weight can all move your size by half a size or more. That's why the evening measurement matters, and why it's worth measuring on a normal day, not straight after a workout or in cold weather. If you're between sizes, go with the larger one for a wide band and the smaller one for a thin band.

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Frequently asked questions

How do I convert a ring size between US, UK and EU?

Every ring size is a way of describing the inside circumference of the ring. EU sizes are simply that circumference in millimetres (a size 54 ring is 54 mm around inside). US sizes count up from a diameter of 11.63 mm in steps of 0.8128 mm, UK sizes use letters from A in steps of 1.25 mm, and Japanese sizes count up in steps of a third of a millimetre of diameter. The converter above matches your size to the nearest equivalent in each system.

How do I measure my ring size at home?

Wrap a thin strip of paper or a piece of string around the base of the finger, mark where it overlaps, then measure the length in millimetres. That length is your finger circumference, and it is the number to pick in the converter. Alternatively, measure the inside diameter of a ring that already fits and use the diameter option.

What size is a typical ring?

Many women wear between US 5 and 9 (EU 49 to 59), and many men between US 8 and 12 (EU 57 to 67). The average is a guide only, because finger size varies from person to person and from day to day.

Should I size up or down if I am between sizes?

Fingers swell with heat, salt and time of day, so measure in the evening at a normal temperature. If you fall between two sizes, choose the larger one for a wide band, since wide bands fit more tightly than thin ones, and the smaller one for a thin band.