Ring Size Chart
Convert ring sizes between US, UK, ISO (EU), Swiss and German systems, or get your size from a ring's diameter or finger circumference.
A finger circumference measured with string or paper is the ISO size in mm.
Measure at room temperature; fingers change size with heat and time of day.
Inner circumference 54.4 mm · diameter 17.3 mm
US 7 · UK N½ · EU 54.4
| US / Canada / Mexico | 7 |
| UK / Ireland / Australia / NZ | N½ |
| ISO 8653 (France, Nordics, much of Europe) | 54.4 |
| Italy / Spain / Switzerland | 14.4 |
| Germany / Netherlands (diameter, mm) | 17.3 |
| Inner diameter | 17.3 mm (0.681 in) |
| US | UK | Circumference (mm) | Diameter (mm) |
|---|---|---|---|
| 3 | F½ | 44.2 | 14.1 |
| 4 | H½ | 46.7 | 14.9 |
| 5 | J½ | 49.3 | 15.7 |
| 6 | L½ | 51.8 | 16.5 |
| 7 | N½ | 54.4 | 17.3 |
| 8 | P½ | 56.9 | 18.1 |
| 9 | R½ | 59.5 | 18.9 |
| 10 | T½ | 62 | 19.7 |
| 11 | V½ | 64.6 | 20.5 |
| 12 | X½ | 67.1 | 21.4 |
| 13 | Z½ | 69.7 | 22.2 |
What this page cannot tell you
Jewellers' sizing tools differ slightly, and US sizes were never set by a precise national standard. India, Japan and China use their own non-linear scales, which are not converted here. A jeweller's sizer on the actual finger is the most reliable measure.
How to find and convert a ring size
- Choose what you know. A US or UK size, ISO circumference, Swiss size, or a ring's inner diameter.
- Enter it. US quarter sizes and UK half sizes are fine.
- Read every system. And the circumference and diameter in mm.
- Check the chart. US sizes 3 to 13 with UK letters and measurements.
10 times a ring size conversion helps
Buying an engagement ring abroad
A buyer converts a US 6 to a UK letter for a London jeweller.
Surprise rings
Someone measures a ring that fits and finds its size.
Online jewellery shops
A shopper converts EU sizes on a European site.
Wedding bands
A couple converts sizes for a jeweller in another country.
Smart rings
A buyer checks a size before ordering.
Resizing
Someone tells a jeweller the size to resize to.
Gift sets
A gift giver converts a size from a list.
Measuring with string
A finger circumference in mm gives the ISO size.
Selling rings
A seller lists a ring's size in several systems.
Comparing charts
Someone checks a store chart against the standard.
How the ring sizes are converted
The page works from the ring's inner circumference. ISO 8653 sizes are the inner circumference in mm. US, Canada and Mexico sizes follow circumference = 2.55 × size + 36.5 mm. UK, Ireland and Australia use letters: since BS 6820:1987 each letter is 1.25 mm of circumference, with C = 40 mm. Italian, Spanish and Swiss sizes are circumference − 40; German and Dutch sizes are the inner diameter in mm. These relations are given in the Wikipedia article on ring size.
Limits: sizing tools differ slightly between jewellers. India, Japan and China use non-linear scales not converted here. Fingers change size with temperature and time of day; a jeweller's sizer is the most reliable measure.
Sources
Frequently asked questions
What is a US size 7 in UK?
N½, about 54.4 mm inner circumference.
How do I find my ring size at home?
Measure the inside diameter of a ring that fits, or wrap string around the finger and measure its length in mm (the ISO size).
Can I convert Indian or Japanese ring sizes?
Not here. Those scales do not change in equal steps, so they cannot be converted with a formula.
What is EU size 52 in US?
About US 6.
How do I convert ring diameter to size?
Choose 'Inner diameter' and enter it in mm.
Are Swiss and Italian sizes the same?
Yes, both are the circumference minus 40.
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