Ring Size Chart and How to Measure Your Ring Size: US, UK and mm
US size 8, UK size P½ and EU size 57 are almost exactly the same ring. The first is an American number, the second a British letter, the third a circumference in millimeters, and in the Netherlands the same ring is called size 18, after its inner diameter. Mix them up and you are easily a whole size out. This page shows how to measure your ring size, a ring size chart that puts every notation side by side, and which size to choose with us when your measurement falls between two sizes.
All our rings come in US sizes without half sizes: the signet rings in 6 through 10, the Cuban ring, the Ice Blox and the box ring in 7 through 11, the moissanite rings between 5 and 9. Two of those sizes are 0.81 mm (0.03in) apart in diameter. That is exactly the margin a careful measurement at home achieves, and a sloppy one misses.
1. Four notations for the same ring
The US size. A number, where every whole step is 0.81 mm of diameter and 2.55 mm of circumference. Size 8 is 18.1 mm (0.71in) in diameter and 57.0 mm in circumference. Half sizes exist, but we only stock whole sizes.
The UK size. A letter, from A to Z and beyond, with half sizes in between. Every whole letter is about 1.25 mm of circumference, so two UK letters are roughly one US size: US 8 is P½, US 9 is R½.
Circumference, the EU size. The length of the inside all the way around, in millimeters. Most shops in France and Belgium and many in Germany call that "size 57", and it is also what you measure with a strip of paper.
Inner diameter. The distance across the inside, from edge to edge. A Dutch or Swedish jeweler who says "size 18" means 18 mm in diameter.
Converting takes one number: circumference is diameter times 3.14. A rule of thumb to recognize a metric size: a number from 15 to 23 is a diameter, a number from 44 to 75 a circumference. Watch out for an Italian or Spanish size: that is the circumference minus 40, so size 17 there is 57 mm of circumference, which is US 8.
2. Ring size chart: US, UK, diameter and circumference
This ring size chart runs from US size 5 to 13, the range almost all adult fingers fall into. The UK letter is the nearest half size, as British jewelers write it; above US 11 the published charts differ by half a letter. The circumference rounded to a whole millimeter is the EU size.
| US size | UK size | Inner diameter | Diameter in inches | Circumference (EU size) | In this size with us |
|---|---|---|---|---|---|
| 5 | J½ | 15.7 mm | 0.62in | 49.3 mm (49) | moissanite ring |
| 6 | L½ | 16.5 mm | 0.65in | 51.9 mm (52) | signet rings, moissanite ring |
| 7 | N½ | 17.3 mm | 0.68in | 54.4 mm (54) | all eight rings |
| 8 | P½ | 18.1 mm | 0.71in | 57.0 mm (57) | all eight rings |
| 9 | R½ | 18.9 mm | 0.75in | 59.5 mm (60) | all eight rings |
| 10 | T½ | 19.8 mm | 0.78in | 62.1 mm (62) | signet rings, Cuban ring, Ice Blox, box ring |
| 11 | V½ | 20.6 mm | 0.81in | 64.6 mm (65) | Cuban ring, Ice Blox, box ring |
| 12 | X½ to Y | 21.4 mm | 0.84in | 67.2 mm (67) | not available |
| 13 | Z½ to Z+1 | 22.2 mm | 0.87in | 69.7 mm (70) | not available |
Necklaces and bracelets are measured differently. Those sizes are in find your size.
3. Ring size conversion: from millimeters to US size
A circumference in millimeters hardly ever lands exactly on a US size, because those steps are 2.55 mm apart. This table converts every circumference from 50 to 66 mm into the size to choose with us. The "exact" column shows how far you are from a whole size.
| Finger circumference | Inner diameter | Exact US size | Narrow band, signet, stone | Wide band: Cuban, Ice Blox, box |
|---|---|---|---|---|
| 50 mm | 15.9 mm (0.63in) | 5.3 | 5 | below 7 |
| 51 mm | 16.2 mm (0.64in) | 5.7 | 6 | below 7 |
| 52 mm | 16.6 mm (0.65in) | 6.1 | 6 | below 7 |
| 53 mm | 16.9 mm (0.66in) | 6.4 | 6 | 7 |
| 54 mm | 17.2 mm (0.68in) | 6.8 | 7 | 7 |
| 55 mm | 17.5 mm (0.69in) | 7.2 | 7 | 8 |
| 56 mm | 17.8 mm (0.70in) | 7.6 | 8 | 8 |
| 57 mm | 18.1 mm (0.71in) | 8.0 | 8 | 8 |
| 58 mm | 18.5 mm (0.73in) | 8.4 | 8 | 9 |
| 59 mm | 18.8 mm (0.74in) | 8.8 | 9 | 9 |
| 60 mm | 19.1 mm (0.75in) | 9.2 | 9 | 10 |
| 61 mm | 19.4 mm (0.76in) | 9.6 | 10 | 10 |
| 62 mm | 19.7 mm (0.78in) | 10.0 | 10 | 10 |
| 63 mm | 20.1 mm (0.79in) | 10.4 | 10 | 11 |
| 64 mm | 20.4 mm (0.80in) | 10.8 | 11 | 11 |
| 65 mm | 20.7 mm (0.81in) | 11.1 | 11 | above 11 |
| 66 mm | 21.0 mm (0.83in) | 11.5 | above 11 | above 11 |
The wide column sits a quarter to half a size higher, because a wide band touches more skin and feels tighter (section 8). If you know your size as a diameter, multiply by 3.14: a Dutch size 20 is a diameter of 20 mm and a circumference of 62.8 mm, exactly US 10.3, so size 10 for a narrow band and 11 for a wide one.
4. How to measure ring size with a ring that already fits
This is the most reliable method, because you measure something that has already proven to fit.
- Pick a ring that fits well on the finger the new ring is for, and that is about as wide.
- Lay it flat on a ruler and measure the inner diameter at the widest point, from inner edge to inner edge.
- Measure again, turned a quarter. A ring that has been worn for years is rarely perfectly round: take the average.
- Look the result up in the chart in section 2.
A ruler has a mark every millimeter, so you read it to half a millimeter. That is already 0.6 of a US size. Use the metric side: the 1/16 inch marks on an inch ruler are 1.6 mm apart, almost two US sizes. A caliper measures to 0.1 mm and takes that error out. If you measure a narrow 2 mm band and order a wide Cuban ring, read section 8 as well.
5. Measuring your finger with a strip of paper
If you do not have a ring that fits, measure your finger. This is how to measure your ring size with paper:
- Cut a strip of paper 5 mm (0.2in) wide and 10 cm (4in) long.
- Wrap it straight around the base of your finger, snug but without pinching.
- Use a fine pen to mark where the paper overlaps.
- Measure the length up to the mark in millimeters. That is your circumference, and with it your EU size.
- Slide the strip, at the same length, over your knuckle. If it will not go, your knuckle decides your size.
A piece of string works worse: it stretches and cuts into the skin, so you measure too small. A strip that sits at an angle measures too big. Every millimeter of circumference is 0.4 of a US size, so measure three times and take the average. Look the result up in the table in section 3.
6. Ring sizer, printable sizer or your phone
A plastic ring sizer is a strip you pull around your finger like a belt. It does not stretch and always sits straight, so it is more accurate than paper. A jeweler measures with test rings or a ring mandrel and usually gives you the size as a US or UK size, a diameter or a circumference: the charts above convert any of them.
A printed sizer or an app that draws a circle on your screen is only as good as its scale. A screen or printout that is 5 percent off is already 0.9 mm out at an 18 mm diameter: more than a whole US size. So check the scale with a bank card, which is 85.6 mm (3.37in) wide all over the world. Always print at 100 percent or actual size, never fit to page: that setting often shrinks the page by a few percent, and 3 percent of a 57 mm circumference is 1.7 mm.
7. When to measure, and what your knuckle does
Fingers are thicker in the evening and in the heat than in the morning and in the cold, by up to about half a size. So measure at the end of the day at room temperature, not right after exercise or a hot shower. Measure in winter with cold hands and you buy a ring that pinches in summer.
Measure the finger the ring is really for. In right-handed people the right hand is often slightly thicker, and a signet ring on the little finger needs its own measurement: never copy the size of your ring finger.
A ring has to go over your knuckle and then stay put at the base. So measure both. If your knuckle is more than 2.5 mm thicker in circumference than the base, a whole US size, the knuckle decides the size and the ring sits slightly loose at the base. That is normal. In that case a wide band is a better choice than a ring with a heavy head: a wide band turns less.
8. Wide rings, signet rings and rings with a stone
A wide band without a head, such as the Cuban ring or an iced out ring, slides over more skin and feels tighter than a narrow band at the same diameter. Jewelers allow a quarter to half a size extra for bands of 8 mm and wider. Because we do not stock half sizes, that is built into the wide column of the table in section 3: if in doubt, take the larger size.
A signet ring has a heavy, flat head. If it sits too loose, the head turns to the side and the engraving disappears from view. The same goes for a ring with a single stone, such as the moissanite ring, and for the moissanite tennis ring, whose stones would otherwise rub against your other fingers. For these rings, choose the smallest size that still slides smoothly over your knuckle.
Having it engraved? Measure first and engrave afterwards: an engraved ring is made for you and cannot be returned. What fits on the head is in ring engraving ideas.
9. Men's ring size: what men wear
Dutch jewelers see most men at a circumference of 57 to 62 mm, US size 8 to 10 or UK P½ to T½. Among our customers it is slightly lower. Size 8 is our most ordered ring size, good for one in three rings, and size 9 comes second. Two in three rings of the past twelve months were size 7, 8 or 9: a diameter of 17.3 to 18.9 mm.
That is a starting point to check your measurement against, not a reason to guess. If you end up at 52 mm or 66 mm, measure again: it can be right, but it falls outside what most men wear. If it still does not fit, you can exchange an unworn ring in its original packaging within 14 days of receipt.
Buying a ring as a gift? Secretly borrow a ring he wears on the same finger and measure it as in section 4. If that is not possible, give a necklace or bracelet instead: our Christmas gift guide explains how to find out those sizes without him noticing.
Where to start
If you want a ring with an engraving, start with the silver-colored signet ring: it engraves more sharply than the gold-colored one, because there is no coating on it. Both are among the signet rings in size 6 through 10. If you want a ring that stands out on its own, look at the gold-colored Cuban ring or the iced out box ring, in size 7 through 11. Measure first, at the end of the day, with paper or with a ring that already fits, and look your size up in the chart at the top.
Frequently asked questions
How do I read a ring size chart?
Find your measurement in the column you have: the inner diameter if you measured a ring, the circumference if you measured your finger. That row gives your US and UK size. US size 8, for example, is 18.1 mm in diameter, 57.0 mm in circumference and UK P½.
How do I measure my ring size at home?
Measure the inner diameter of a ring that already fits, at the widest point. If you do not have one, wrap a 5 mm wide strip of paper around your finger, mark the overlap and measure the length: that is your circumference. Divide by 3.14 for the diameter.
What is the average ring size for men?
Most men wear a circumference of 57 to 62 mm, US size 8 to 10 or UK P½ to T½. At Carpe Ice, size 8 is the most ordered ring size, and two in three rings of the past twelve months were size 7, 8 or 9.
What is US size 9 in UK sizes?
US size 9 is UK R½: an inner diameter of 18.9 mm and a circumference of 59.5 mm. US 7 is N½, US 8 is P½, US 10 is T½ and US 11 is V½.
What do I do if I am between two sizes?
With a wide band, such as a Cuban ring or iced out ring, take the larger size: a band of 8 mm or wider needs a quarter to half a size extra. With a signet ring or a ring with a stone, take the smallest size that still slides smoothly over your knuckle.
Is ring size 57 the same as US size 8?
Almost. Size 57 is a circumference of 57 mm and a diameter of 18.1 mm: US size 8. A Dutch size 18 is a diameter of 18.0 mm, exactly US 7.8, so size 8 with us as well. The difference is 0.1 mm, less than you can measure at home.
Can I measure my ring size with my phone?
Only if you check the scale. A screen that is 5 percent off is already 0.9 mm out at 18 mm, more than a whole size. Lay a bank card on the screen: it is 85.6 mm wide. If that does not match, do not trust the measurement.