ring size chart & calculator
Measure your finger or a ring you already own, and get your size in US, UK, EU, Japanese and Swiss systems at once. There’s a printable sizer too if you don’t have a tape measure.
fashion law journal · tools deskupdated 25 sep 2026based on iso 8653
Quick answer: ring size is the inner circumference of the ring. A US size 7 measures 54.4 mm around (17.3 mm across), which is a UK N½ and an EU 54. Each whole US size adds about 2.55 mm of circumference.
Wrap a strip of paper or string around the base of your finger, mark where it overlaps, and measure that length flat against a ruler.
Lay a ring that fits the same finger on a ruler and measure straight across the inside edge to inside edge, at the widest point.
your size
Enter a measurement to see your size in every system.
ring size conversion chart
EU sizes follow ISO 8653, where the size number is simply the inner circumference in millimetres. Swiss sizes are that figure minus 40. US and UK sizes are jewellers’ scales that don’t map one-to-one, so UK sizes usually land on a half letter.
| US / CA | UK / AU | EU / ISO | Japan | Swiss | diameter | circumference |
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how to measure your ring size at home
- cut a stripUse a thin strip of paper about 10 cm long. String works, but it stretches, so paper is more accurate.
- wrap the baseWrap it snugly around the base of the finger you’re sizing. It should slide over the knuckle without forcing.
- mark the overlapMark the point where the paper meets itself with a fine pen.
- measure flatLay the strip against a ruler and read the length in millimetres. Enter it above as your circumference.
Already own a ring that fits? Measuring its inside diameter is more reliable than any string method. Use the a ring I own tab above.
five things that change your size
- Temperature. Fingers shrink in the cold and swell in the heat. Measure at room temperature, ideally in the afternoon.
- Your knuckle. If your knuckle is much wider than the base of your finger, size for the knuckle or the ring won’t go on.
- Band width. Wide bands (6 mm and up) sit tighter. Go up a quarter to half a size.
- Which hand. Your dominant hand is usually slightly larger, so measure the actual finger the ring is for.
- Measure twice. Take readings on two different days and use the larger one if they differ.
buying online: resizing and returns
Get the size right before you order, especially for engraved or made-to-order pieces. In the UK and EU you normally have 14 days to cancel an online purchase, but goods made to your specifications or clearly personalised (engraving, custom sizing) are exempt from that right.
In the US there’s no general federal right to return, so the retailer’s own policy governs. Eternity bands and some tension-set or patterned rings can’t be resized at all, so check before you buy.
ring size questions
What is the average ring size?
The sizes most often quoted are around US 6 to 7 for women and US 9 to 10 for men. Treat these as rough starting points only. Hands vary a lot, and a guess can easily be off by two sizes.
Are UK and US ring sizes the same?
No. The US uses numbers and the UK and Australia use letters. A US 7 is roughly a UK N½, and a US 9 is roughly a UK R½. Use the chart above to convert.
How accurate is the string method?
It’s usually within half a size, but string stretches and can compress skin. A paper strip is better, and measuring an existing ring’s inside diameter is better still.
What if I’m between two sizes?
For narrow bands, pick the size closest to your measurement. For wide bands, or if your knuckle is large, go up to the next half size.
How do I convert millimetres to a ring size?
If you measured circumference, the EU size is the millimetre figure rounded. For the US size, subtract 36.5 and divide by 2.55. For a diameter, multiply it by 3.1416 to get the circumference first. The calculator above does all of this for you.
How can I find someone’s ring size without asking?
Borrow a ring they wear on the same finger and measure its inside diameter, or press it into a bar of soap to take an impression you can measure later. If you have to guess, go slightly larger. Sizing down is usually easier than sizing up.
Conversions follow ISO 8653 and standard US and UK jewellers’ scales. Individual brands can differ by up to half a size, so check the jeweller’s own chart before ordering a custom or non-returnable piece. This page is general information, not legal advice. More from FLJ: care label symbol decoder · global trademark search directory.