Ring Size Calculator | Find your ring size accurately

Find your ring size from a diameter, a circumference or a size in any system. Converts between US, UK, EU, Japan and Swiss sizes, with a printable ring sizer you can check for scale.


What do you have?
Measure straight across the inside of a ring that already fits.
Clear

Printable ring sizer

Print this page at 100% scale, with no page fitting or shrinking, then use either guide below. Check the calibration bar first.

Check the scale first

This bar must measure exactly 50 mm on paper. If it does not, your printer scaled the page and the guides below will be wrong.

50 mm exactly

Guide 1: match an existing ring

Place a ring you already wear over the circles until the inner edge of the ring lines up with a circle.

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Guide 2: wrap around your finger

Cut along the strip, wrap it round the base of your finger and read the size where the end meets.

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Full ring size conversion chart

Diameter and circumference for every common size, across all five sizing systems.

US / CanadaUK / AustraliaEU / ISOJapan / ChinaSwitzerland Diameter (mm) Circumference (mm)
3 F 44.3 4 4.3 14.1 44.3
3.5 G 45.6 5 5.6 14.5 45.6
4 H½ 46.8 6.5 6.8 14.9 46.8
4.5 I½ 48.1 8 8.1 15.3 48.1
5 J½ 49.3 9 9.3 15.7 49.3
5.5 K½ 50.6 10 10.6 16.1 50.6
6 L½ 51.8 11.5 11.8 16.5 51.8
6.5 M½ 53.1 13 13.1 16.9 53.1
7 N½ 54.3 14 14.3 17.3 54.3
7.5 O½ 55.6 15 15.6 17.7 55.6
8 P½ 56.9 16 16.9 18.1 56.9
8.5 Q½ 58.1 17 18.1 18.5 58.1
9 R½ 59.4 18 19.4 18.9 59.4
9.5 S½ 60.9 19 20.9 19.4 60.9
10 T½ 62.2 20 22.2 19.8 62.2
10.5 U½ 63.5 22 23.5 20.2 63.5
11 V½ 64.7 23 24.7 20.6 64.7
11.5 W½ 66.0 24 26.0 21.0 66.0
12 X½ 67.2 25 27.2 21.4 67.2
12.5 Y½ 68.5 26 28.5 21.8 68.5
13 Z½ 69.7 27 29.7 22.2 69.7
13.5 Z+1 71.0 28 31.0 22.6 71.0
14 Z+2 72.3 29 32.3 23.0 72.3

How ring sizing actually works

Every ring sizing system in the world describes the same thing: the inside of the band. Some countries state it as a diameter, some as a circumference, and some as an arbitrary number or letter on a scale. That is why a US 7 equals a UK N and a half, an EU 54 and a Japanese 14. They are all the same ring.

Measuring accurately at home

The most reliable method is measuring a ring that already fits on the right finger, straight across the inside. Measuring the finger itself with paper or string works but is easier to get wrong, because paper stretches and string tightens. If you use the finger method, wrap it snugly rather than tightly and take the reading where the paper first overlaps.

When to measure

Fingers change size through the day and the year. They are smallest in the morning and in cold weather, and largest in the evening, in heat, and after exercise or salty food. Measure at the end of a normal day at room temperature, and if you can, measure two or three times on different days and take the average.

Practical advice

  • A ring has to pass the knuckle. If your knuckle is much wider than the base of your finger, size up so it slides on, then consider having the band adjusted.
  • Wide bands feel tighter than thin ones. For a band over about 6 mm wide, go up a quarter to a half size.
  • If a measurement lands between two sizes, choose the larger one. A slightly loose ring can be resized down more easily than a tight one can be stretched.
  • Your dominant hand is usually a little larger, so measure the exact finger the ring is for.
  • Never measure a cold finger, and take rings off before measuring the finger next to them.

Frequently asked questions

The most accurate way is to take a ring that already fits the right finger and measure straight across the inside with a ruler, in millimetres. Enter that diameter above. If you have no ring to measure, wrap a strip of paper around the base of the finger, mark where it overlaps, lay it flat and measure the length. That is the circumference, which this calculator also accepts.

A 17 mm inner diameter is a US size 6.5, a UK M and a half, an EU 53.4 and a Japanese 13. Enter any diameter above and the calculator returns the size in all five systems at once, along with the exact circumference.

UK sizes use letters, and each US whole size is roughly one and a half letters. A US 6 is a UK L and a half, a US 7 is a UK N and a half, and a US 8 is a UK P and a half. Because neither scale is truly continuous, use the conversion chart on this page rather than adding a fixed offset.

It is, provided your printer does not scale the page. Print at 100% with page fitting turned off, then check the calibration bar with a ruler: it must measure exactly 50 mm. If it does not, the whole sheet is scaled and every circle on it will be the wrong size.

Go up rather than down. A ring that is slightly loose is still wearable and can be sized down cheaply, whereas one that will not pass the knuckle is unwearable and stretching a band is limited and risky. Wide bands in particular should be taken up a quarter to a half size.

Late in the day at normal room temperature. Fingers are smallest first thing in the morning and in the cold, and can swell noticeably in heat, after exercise, or after salty food. Measuring once in the morning is the most common reason a ring turns out too tight.

Yes. A wide band covers more of the finger and sits with less room to move, so it feels tighter than a narrow one of the same size. For bands wider than about 6 mm, most jewellers suggest going up a quarter to a half size.

It is simply the inner circumference in millimetres, which is why it looks like a plausible measurement rather than an arbitrary number. An EU 54 ring measures 54 mm around the inside. That makes it the easiest system to check against a measurement you have taken yourself.

How do you find your ring size?

Measure the inner diameter of a ring that already fits, in millimetres, and enter it above. A 17 mm diameter is a US 6.5, a UK M½, an EU 53 and a Japanese 13. If you have no ring to measure, use the finger circumference instead, or print the sizer further down the page at 100% scale.