Ring Size Calculator
Convert ring measurements between US, UK, and EU sizes from diameter or circumference.
By Konstantin Iakovlev · Updated April 2026 · Source: BLS
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
Ring sizing runs on different standards in the US, UK, and EU, and converting between them is straightforward once you have either the band's diameter or its circumference. The stakes have grown as jewelry shopping goes global: roughly 35% of all ring purchases in 2026 are expected to cross borders, and a wrong size means a costly return and the waste of shipping a second piece. Getting the fit right the first time keeps both the buyer and the planet better off.
Conversions here draw on recognized international sizing charts paired with direct math. To move from diameter (D) to circumference (C), the relationship is C = πD; going the other way, D = C/π. Those figures are then matched against current 2026 sizing tables for the US numerical scale, the UK alphabetical scale, and the EU system measured by circumference in millimeters, and the nearest standard size is returned.
Measure with a flexible tape or a length of string, snug against the finger without pinching. Finger size drifts over the course of a day and with temperature, so the most reliable reading comes in the evening when fingers tend to be warmest. Resist the urge to round too hard, because even a fraction of a millimeter can push you into a different ring size entirely.
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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