Ring Size Converter: Convert Between US, UK, EU, and Measurement-Based Sizes
Buying jewelry online or internationally? Ring sizes vary significantly between countries, and wearing the wrong size is uncomfortable or even risky (rings can slip off or cut off circulation). Our converter handles all three major sizing systems — US, UK, and EU — plus direct conversion from diameter or circumference measurements.
The complete size chart lets you cross-reference any size at a glance.
Ring size measurement formulas:
Ring Sizing Systems Compared
US/Canada System: Numeric, half-size increments (3 to 13). Based on inner circumference. Size 6 = 51.9mm circumference, 16.5mm diameter.
UK/Australia System: Alphabetic (F to Z+). Each letter = approximately 1.25mm difference in circumference. UK N (US 7) is the most common women's size.
EU/ISO System: Inner circumference in mm (44 to 70+). The most logical system - directly measurable. EU 54 = exactly 54mm inner circumference.
How to Measure at Home
String method: Wrap a thin string around your finger, mark the overlap, measure the length - this is your circumference in mm. Look up in the chart.
Existing ring method: Measure the inner diameter with a ruler or calipers, enter it in the Diameter field above.
Tips for accuracy: Measure at end of day, at normal temperature, on the specific finger you plan to wear the ring on.
Practical Examples
Buying a ring from the UK (US customer)
- 1.Know your US size: e.g. US 7
- 2.Convert: US 7 = UK N = EU 54
- 3.Tell the UK jeweler: UK size N
- 4.Or: Give diameter 17.3mm or circumference 54.4mm
Measuring for a surprise gift
- 1.Find an existing ring that fits the right finger
- 2.Measure inner diameter with ruler in mm
- 3.Enter diameter in converter above
- 4.Get all size equivalents for any country
Frequently Asked Questions
How do I convert US ring sizes to UK sizes?
Use the converter above: select US Sizes, choose your size, and the equivalent UK letter size appears instantly. US size 7 = UK N, US size 8 = UK P, US size 9 = UK R, US size 10 = UK T. UK sizes use letters (F through Z+) while US uses numbers (3 through 13 in half-size increments).
What is EU ring size and how is it measured?
EU (European) ring sizes are based on the inner circumference of the ring in millimeters. EU size 54 means the inner circumference is 54mm. This is also the ISO standard and is used across most of continental Europe, including France, Germany, Spain, and Italy. EU sizes range from about 44 to 70 for standard ring sizes.
How do I measure my ring size at home?
Method 1 - Measure an existing ring: Use a ruler to measure the inner diameter in mm, then look up in the chart. Method 2 - Measure your finger: Wrap a thin strip of paper around your finger, mark where it overlaps, measure the length (this is your circumference in mm), then look up in the chart. Measure at end of day when fingers are largest.
Why do ring sizes differ between countries?
Different countries developed their own ring sizing systems independently. The US and Canada use a numeric system starting at size 3. The UK and Australia use letters (A through Z+). Continental Europe uses ISO 8653 which measures inner circumference in mm. Japan and Asia use a different numeric system. Always specify the system when ordering internationally.
What is the most common ring size for women?
In the US, the most common women's ring size is 6-7 (UK N-P, EU 52-54). The average women's ring size is approximately 6.5 US. For engagement rings, US size 6 (UK L-M, EU 52) is the most purchased size.
What is the most common ring size for men?
In the US, the most common men's ring size is 9-10 (UK R-T, EU 60-62). The average men's ring size is approximately 9-9.5 US. Wedding bands for men are most commonly ordered in sizes 9-10.
Why should I measure at end of day?
Fingers swell throughout the day due to activity, temperature, and fluid retention. They are smallest in the morning when cold and largest in the evening. Measuring at the end of the day ensures your ring will always fit comfortably. Also measure in warm conditions rather than cold.
What if I am between ring sizes?
If you are between sizes, generally go up to the larger size rather than down. This is especially important for rings with thicker bands (over 6mm wide) which need to slide over the knuckle. You can always have a ring sized down by a jeweler, but sizing up on a gemstone ring can be more complex.