How to Use This Chart
This ring size conversion chart makes it easy to find your size across multiple sizing systems. Whether you're measuring a ring at home or shopping internationally, use these steps to find your perfect fit:
- 1 Measure the inner diameter of a ring that fits you well (use a ruler or digital caliper). Measure in millimeters for best accuracy.
- 2 Find your diameter measurement in the chart below (look in the "Inner Diameter" column).
- 3 Read across the row to find your size in any country's system — US, UK, Europe, Japan, Australia, Germany, or Switzerland.
- 4 Use the circumference column if you're measuring around the ring instead of across it.
Ring Size Conversion Table
| US/Canada | UK/Ireland | Europe | Japan | Australia | Inner Diameter (mm) | Inner Circumference (mm) |
|---|---|---|---|---|---|---|
| US 3 | F½ | 44 | 4 | F½ | 14.1 | 44.2 |
| US 3.5 | G½ | 45.5 | 5 | G½ | 14.5 | 45.5 |
| US 4 | H½ | 47 | 7 | H½ | 14.9 | 46.8 |
| US 4.5 | I½ | 48 | 8 | I½ | 15.3 | 48.0 |
| US 5 | J½ | 49 | 9 | J½ | 15.7 | 49.3 |
| US 5.5 | K½ | 50.5 | 10 | K½ | 16.1 | 50.6 |
| US 6 | L½ | 51.5 | 12 | L½ | 16.5 | 51.8 |
| US 6.5 | M½ | 52.5 | 13 | M½ | 16.9 | 53.1 |
| US 7 | N½ | 54 | 14 | N½ | 17.3 | 54.4 |
| US 7.5 | O½ | 55.5 | 15 | O½ | 17.7 | 55.7 |
| US 8 | P½ | 57 | 16 | P½ | 18.1 | 56.9 |
| US 8.5 | Q½ | 58 | 17 | Q½ | 18.5 | 58.2 |
| US 9 | R½ | 59 | 18 | R½ | 18.9 | 59.5 |
| US 9.5 | S½ | 60.5 | 19 | S½ | 19.4 | 60.8 |
| US 10 | T½ | 62 | 20 | T½ | 19.8 | 62.1 |
| US 10.5 | U½ | 63 | 22 | U½ | 20.2 | 63.4 |
| US 11 | V½ | 64 | 23 | V½ | 20.6 | 64.6 |
| US 11.5 | W½ | 65.5 | 24 | W½ | 21.0 | 65.9 |
| US 12 | X½ | 67 | 25 | X½ | 21.4 | 67.2 |
| US 12.5 | Y½ | 68 | 26 | Y½ | 21.8 | 68.5 |
| US 13 | Z | 69 | 27 | Z | 22.2 | 69.7 |
| US 13.5 | Z+½ | 70.5 | 28 | Z+½ | 22.6 | 71.0 |
| US 14 | Z+1 | 72 | 29 | Z+1 | 23.0 | 72.3 |
| US 15 | Z+2 | 74.5 | 30 | Z+2 | 23.8 | 74.8 |
Tips for Getting an Accurate Ring Size
Measure at the end of the day
Fingers are slightly larger in the evening due to natural daily swelling. Avoid measuring in the morning when fingers are at their smallest.
Keep room temperature steady
Cold temperatures shrink your fingers, while warm temperatures cause them to expand. Measure when your body is at a comfortable, normal temperature.
Account for dominant hand differences
Your writing hand is typically up to half a size larger than your non-dominant hand. Measure both if you wear rings on both hands.
Size up for wide bands
Wide bands feel tighter than thin bands at the same size. If buying a wide band (6mm or more), consider sizing up by half a size for comfort.
Ring Size by Gender
Ring sizes vary considerably by gender, though there is overlap. Here are average sizes based on typical hand proportions:
Women's Sizes
- • Average size: US 6–7
- • Common range: US 4–9
- • Diameter: 16.5–17.3mm
Men's Sizes
- • Average size: US 9–10
- • Common range: US 8–12
- • Diameter: 18.1–20.6mm
Frequently Asked Questions
What's the difference between inner diameter and circumference? +
The inner diameter is the straight measurement across the inside of the ring from one edge to the opposite edge, passing through the center. The inner circumference is the distance around the inside of the ring (like measuring a circle's perimeter). You can use either measurement to find your size — they correspond to the same ring size.
Can I get a half size if my measurement is between sizes?
+
Yes, most jewelers offer half sizes. If your measurement falls between two sizes (for example, between US 7 and US 7.5), you can order a half size. If the jeweler doesn't offer half sizes, consider rounding up slightly for a more comfortable fit.
Yes, most jewelers offer half sizes. If your measurement falls between two sizes (for example, between US 7 and US 7.5), you can order a half size. If the jeweler doesn't offer half sizes, consider rounding up slightly for a more comfortable fit.
Why do international ring sizes differ so much? +
Different countries developed their own sizing systems historically, before international standardization. The US uses numbers (3–15+), the UK uses letters, Europe uses numbers from 44–74+, and Asia uses different scales entirely. This chart helps bridge those systems so you can order confidently from anywhere in the world.
Should I size up for a wide band ring? +
Yes, wide bands (6mm or more) feel tighter than thin bands at the same measured size. Consider sizing up by half a size to a full size for wide band rings to ensure comfort and ease of movement on your finger.
How do I use the Ring Sizer app to measure? +
Simply place an existing ring that fits you well flat on your iPhone screen, and the app will measure its inner diameter instantly. It then converts to your size in every system — US, UK, EU, Japan, Australia, and more. It's fast, free, and accurate.
