Ring size converter: US, Europe, Japan and UK sizes
Enter the size you know or the ring's measurement in millimetres and get the equivalent in every system. The full ring size chart sits below, ready for the counter.
Free, no sign-up. Everything is calculated in your browser.
Ring size converter
Choose what you know: a size or the measurement in millimetres.
Equivalents
- US and Mexico
- 7
- Europe (ISO)
- 54
- United Kingdom
- N½
- Japan
- 14
- Inside diameter
- 17.3 mm
- Inside circumference
- 54.4 mm
Ring size chart
| US / MX | Diameter | Circ. | Europe | UK | Japan |
|---|---|---|---|---|---|
| 3 | 14.1 mm | 44.2 mm | 44 | F½ | 4 |
| 3.5 | 14.5 mm | 45.5 mm | 45 | G½ | 5 |
| 4 | 14.9 mm | 46.8 mm | 47 | H½ | 7 |
| 4.5 | 15.3 mm | 48.0 mm | 48 | I½ | 8 |
| 5 | 15.7 mm | 49.3 mm | 49 | J½ | 9 |
| 5.5 | 16.1 mm | 50.6 mm | 51 | K½ | 10 |
| 6 | 16.5 mm | 51.9 mm | 52 | L½ | 12 |
| 6.5 | 16.9 mm | 53.1 mm | 53 | M½ | 13 |
| 7Your size | 17.3 mm | 54.4 mm | 54 | N½ | 14 |
| 7.5 | 17.7 mm | 55.7 mm | 56 | O½ | 15 |
| 8 | 18.1 mm | 57.0 mm | 57 | P½ | 16 |
| 8.5 | 18.5 mm | 58.2 mm | 58 | Q½ | 18 |
| 9 | 18.9 mm | 59.5 mm | 60 | R½ | 19 |
| 9.5 | 19.4 mm | 60.8 mm | 61 | S½ | 20 |
| 10 | 19.8 mm | 62.1 mm | 62 | T½ | 21 |
| 10.5 | 20.2 mm | 63.3 mm | 63 | U½ | 22 |
| 11 | 20.6 mm | 64.6 mm | 65 | V½ | 24 |
| 11.5 | 21.0 mm | 65.9 mm | 66 | W½ | 25 |
| 12 | 21.4 mm | 67.2 mm | 67 | X½ | 26 |
| 12.5 | 21.8 mm | 68.5 mm | 68 | Z | 27 |
| 13 | 22.2 mm | 69.7 mm | 70 | Z+1 | 29 |
How to find a ring size
- 1.If you have a ring that fits, measure its inside diameter with calipers, edge to edge on the inside.
- 2.With no ring at hand, wrap a thread or a strip of paper round the base of the finger, mark where it meets and measure that length: it is the circumference.
- 3.Choose diameter or circumference in the calculator and enter the millimetres.
- 4.If you already know the size in another country's system, choose that system and the size.
- 5.Read the equivalent in US and Mexico, Europe, the UK and Japan.
How ring size systems relate
Every system measures the same thing, the inside of the ring, but numbers it differently. US sizes, also used in Mexico, start at size 0 = 11.63 mm across and add 0.81 mm of diameter per size.
In Europe the size is the inside circumference in millimetres: a size 54 measures 54 mm round the inside. UK sizes are letters from A to Z with half sizes in between. In Japan each size adds a third of a millimetre of diameter.
That is why printed charts disagree: every maker rounds its own way. The calculator starts from the millimetres and converts them to each system, so treat it as a guide and confirm with a ring sizer for an engagement piece.
Fingers swell in the heat and later in the day, and a wide band (over 6 mm) feels tighter: in those cases go up half a size.
Frequently asked questions
What is a US size 7 ring in European sizes?
A US size 7 is about 17.3 mm across and 54.4 mm round the inside: a 54 in Europe, N½ in the UK and 14 in Japan.
Are Mexican ring sizes the same as US sizes?
Yes. Jewelers in Mexico use the US numbering, with whole, half and sometimes quarter sizes.
How can I measure my ring size at home?
Wrap a thread round the base of the finger, mark where it meets, measure the length with a millimetre ruler and enter it as the circumference. Measure in the afternoon and make sure the thread clears the knuckle.
What is the most common ring size?
For women, between US 5 and 7; for men, between 8 and 11. For a gift when you don't know the size, 6 and 9 respectively are reasonable bets that are easy to resize.
Can a ring be made bigger or smaller?
Most plain gold or silver rings can be resized one or two sizes at the bench. Eternity bands, with stones all the way round, and titanium or tungsten rings can hardly be resized at all.