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Convert between US numeric ring sizes and UK letter sizes with diameter measurements
| US Size | UK Size | Diameter (mm) | Circumference (mm) |
|---|---|---|---|
| 3 | F | 14 | 44 |
| 3.5 | G | 14.4 | 45.2 |
| 4 | H | 14.8 | 46.5 |
| 4.5 | I | 15.3 | 48 |
| 5 | J | 15.7 | 49.3 |
| 5.5 | K | 16.1 | 50.6 |
| 6 | L | 16.5 | 51.9 |
| 6.5 | M | 16.9 | 53.1 |
| 7 | N | 17.3 | 54.4 |
| 7.5 | O | 17.7 | 55.6 |
| 8 | P | 18.1 | 56.9 |
| 8.5 | Q | 18.5 | 58.1 |
| 9 | R | 19 | 59.7 |
| 9.5 | S | 19.4 | 60.9 |
| 10 | T | 19.8 | 62.2 |
| 10.5 | U | 20.2 | 63.5 |
| 11 | V | 20.6 | 64.7 |
| 11.5 | W | 21 | 66 |
| 12 | X | 21.4 | 67.2 |
| 12.5 | Y | 21.8 | 68.5 |
| 13 | Z | 22.2 | 69.7 |
US Ring Sizing: The United States uses a numerical ring sizing system that ranges from approximately 3 to 13.5 for adults. US ring sizes are based on the inner circumference of the ring measured in inches, divided by π (pi), and then multiplied by a constant. Each full size represents a difference of 0.032 inches (0.8128 mm) in diameter.
UK Ring Sizing: The United Kingdom uses an alphabetical sizing system, with letters ranging from A to Z (and beyond with Z+1, Z+2, etc. for larger sizes). The most common adult sizes range from F to Z. Each letter increment represents approximately 1.25 mm in circumference.
Key Differences: The main difference is the notation style - US uses numbers while UK uses letters. However, both systems measure the same physical dimension (the inner diameter of the ring). UK sizes typically start lower in the alphabet for smaller rings, with the mid-range letters (L-Q) being most common for women, and larger letters (S-W) more common for men.
Unlike shoe sizing which can vary by gender, ring sizes are universal - a US size 7 measures the same diameter whether it's for a man or woman. The only difference is the typical range, with women's rings usually falling between US 5-8 (UK J-P) and men's rings between US 8-12 (UK P-X).
Unlike shoe sizes with simple formulas, ring size conversion between US and UK systems requires a reference chart because the relationship isn't linear. The alphabetical UK system doesn't follow a mathematical formula from the US numerical system.
For women in the US, the most common ring size is 6-7 (UK L-N). For men, it's typically 9-10 (UK R-T). However, this varies significantly based on individual finger size and can differ by ethnicity and geography.
Yes, but professional measurement is recommended for expensive purchases. At home, you can use a printable ring sizer, measure an existing ring's inner diameter, or wrap a string around your finger and measure the circumference. Always measure the specific finger you'll wear the ring on, as fingers vary in size.
No, different countries use different sizing systems. Besides US (numerical) and UK (alphabetical), there's also European/French sizing (numbers based on circumference in mm), Japanese sizing (numbers 1-27), and others. Always verify which system a retailer uses.
Yes, rings wider than 6mm should typically be sized up by 0.25-0.5 sizes. Wider bands cover more of your finger and need extra room. Very wide bands (8mm+) may need a full size up. Try on similar width rings when possible.
Finger size can fluctuate up to a half size or more during the day. Fingers are typically smallest in the morning and largest in the evening. They also swell in hot weather and shrink when cold. For best results, measure at different times and temperatures.
If measuring your finger gives a diameter that falls between two standard sizes, it's generally better to choose the larger size. Rings that are too tight are uncomfortable and difficult to remove, while slightly loose rings can be resized down more easily by a jeweler.