Ring Size Calculator
Convert ring measurements between US, UK, and EU sizes from diameter or circumference.
US Size
6.5
UK Size
R
EU Size
53.2
Size Equivalents
| US Size | 6.5 |
| UK Size | R |
| EU Size (circumference mm) | 53.2 |
| Inside Diameter | 16.92 mm |
| Inside Circumference | 53.16 mm |
Reference Chart
| US | UK | EU | Diameter | Circ. |
|---|---|---|---|---|
| 3 | K | 44.1 | 14.05 mm | 44.14 mm |
| 4 | M | 46.7 | 14.86 mm | 46.68 mm |
| 5 | O | 49.3 | 15.70 mm | 49.32 mm |
| 6 | Q | 51.9 | 16.51 mm | 51.87 mm |
| 7 | S | 54.5 | 17.35 mm | 54.51 mm |
| 8 | U | 57.2 | 18.19 mm | 57.15 mm |
| 9 | W | 59.3 | 18.89 mm | 59.34 mm |
| 10 | Y | 62.3 | 19.84 mm | 62.33 mm |
| 11 | [ | 65.0 | 20.68 mm | 64.97 mm |
| 12 | ] | 67.5 | 21.49 mm | 67.51 mm |
| 13 | _ | 70.2 | 22.33 mm | 70.15 mm |
| 14 | a | 72.3 | 23.01 mm | 72.29 mm |
| 15 | c | 74.8 | 23.83 mm | 74.84 mm |
Use the Ring Size Calculator above to calculate your results. Enter your values and see instant results — all calculations run in your browser.
Disclaimer: This calculator is for informational purposes only and does not constitute tax, financial, or legal advice. Results are estimates based on the information you provide and current rates. Always consult a qualified tax professional or financial advisor for advice specific to your situation.
How It Works
This calculator provides a seamless way to convert ring sizes between the US, UK, and EU standards, whether you have the ring's diameter or circumference. With global e-commerce booming, an estimated 35% of all ring purchases in 2026 are expected to be made internationally, making accurate size conversion more critical than ever to avoid costly returns and sizing issues. Ensuring a perfect fit from the start enhances customer satisfaction and reduces environmental impact from shipping multiple items.
Our calculator utilizes established international sizing charts and direct mathematical conversions. For diameter (D) to circumference (C), we use the formula C = πD. Conversely, for circumference to diameter, D = C/π. These calculated values are then cross-referenced with the most current 2026 standardized sizing tables for US (numerical), UK (alphabetical), and EU (circumference-based in mm) systems to provide the closest corresponding size.
When measuring, use a flexible tape measure or string and ensure it's snug but not tight. Remember that finger size can fluctuate throughout the day and with temperature changes, so it's best to measure at the end of the day when your fingers are warmest. A common mistake is rounding measurements too aggressively; even a fraction of a millimeter can alter the ring size significantly.
Example: Converting a Circumference to US, UK, and EU Sizes
- 1 You have a ring that measures 56.5 mm in circumference.
- 2 Input 56.5 mm into the 'Circumference' field. The calculator will then determine the equivalent diameter and match these values against the 2026 international sizing charts.
- 3 The calculator outputs: US Size 7.75, UK Size P 1/2, EU Size 56.5.
- 4 This means a ring with a 56.5 mm circumference perfectly aligns with these specific international sizes, ensuring you can confidently purchase or order a ring in any of these regions.
Source: BLS · Last updated: April 2026
Frequently Asked Questions
How do I find my ring size at home?
What is the most common ring size for women?
How do US ring sizes convert to European sizes?
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