Ring Size Guide
At LUCERARO, we want your ring to fit perfectly. Use this guide to find your US ring size, then convert it to common international sizes. Our sizes follow the standard US system as defined by the Gemological Institute of America (GIA).
How to Measure Your Ring Size
Method 1: Measure an Existing Ring
- Choose a ring that fits the intended finger comfortably.
- Using a millimeter ruler, measure the inside diameter of the ring — the longest distance from one inner edge to the opposite inner edge.
- Match your measurement to the Inside Diameter (mm) column in the chart below.
Note: If your ring is wider than 6mm, we recommend choosing a half size up.
Method 2: Measure Your Finger
- Wrap a piece of non-stretchy string or paper around the base of your finger.
- Mark the point where the string or paper overlaps.
- Lay it flat and measure the length in millimeters — this is your finger circumference.
- Match your measurement to the Inside Circumference (mm) column in the chart below.
Tips for Accurate Measurement
- Measure at the end of the day, when your fingers are at their natural largest.
- Avoid measuring in cold environments or right after exercise.
- Repeat the measurement 2–3 times to ensure consistency.
- If your knuckle is larger than the base of your finger, choose a size that slides comfortably over the knuckle.
- Do not use elastic string — it can stretch and give a smaller measurement.
International Ring Size Conversion Chart
Find your US size in the first column, then read across for equivalent sizes in other regions. All measurements are based on ISO 8653:2016 .
| US Size |
Inside Dia. (mm) |
Inside Circum. (mm) | UK/AU | EU | JP | HK | Swiss |
|---|---|---|---|---|---|---|---|
| 3 | 14.1 | 44.2 | F | 44 | 4 | 6 | 4 |
| 3¼ | 14.3 | 44.8 | F½ | 45 | 5 | — | 5¼ |
| 3½ | 14.5 | 45.5 | G | 45.5 | 6 | 7.5 | — |
| 3¾ | 14.7 | 46.1 | G½ | 46 | 7 | — | 6½ |
| 4 | 14.8 | 46.8 | H½ | 47 | 8 | 9 | 7½ |
| 4¼ | 15.0 | 47.4 | I | 47.5 | — | — | — |
| 4½ | 15.3 | 48.0 | I½ | 48 | 8 | 10 | — |
| 4¾ | 15.5 | 48.7 | J | 48.5 | — | — | 9 |
| 5 | 15.7 | 49.3 | J½ | 49 | 9 | 11 | 10 |
| 5¼ | 15.9 | 50.0 | K | 50 | — | 12 | 10 |
| 5½ | 16.1 | 50.6 | K½ | 50.5 | 10 | 12 | 11¼ |
| 5¾ | 16.3 | 51.2 | L | 51 | 11 | 13 | 12¼ |
| 6 | 16.5 | 51.9 | L½ | 52 | 12 | 13 | 12¾ |
| 6¼ | 16.7 | 52.5 | M | 52.5 | 13 | 14.5 | 14 |
| 6½ | 16.9 | 53.1 | M½ | 53 | 13 | 14.5 | 14 |
| 6¾ | 17.1 | 53.8 | N | 54 | — | 15 | 15¾ |
| 7 | 17.3 | 54.4 | N½ | 54.5 | 14 | 16 | 15¼ |
| 7¼ | 17.5 | 55.1 | O | 55 | 15 | 17 | 16¼ |
| 7½ | 17.7 | 55.7 | O½ | 55.5 | 15 | 17 | 16½ |
| 7¾ | 17.9 | 56.3 | P | 56 | 16 | 18 | 17¼ |
| 8 | 18.1 | 57.0 | P½ | 57 | 16 | 18 | 17¾ |
| 8¼ | 18.3 | 57.6 | Q | 57.5 | 17 | 19 | 18¼ |
| 8½ | 18.5 | 58.3 | Q½ | 58 | 17 | 19 | 18½ |
| 8¾ | 18.8 | 58.9 | R | 59 | 18 | 19 | 19 |
| 9 | 19.0 | 59.5 | R½ | 59.5 | 18 | 20.5 | 20 |
| 9¼ | 19.2 | 60.2 | S | 60 | 19 | 20.5 | 20¼ |
| 9½ | 19.4 | 60.8 | S½ | 61 | 19 | 22 | 21 |
| 9¾ | 19.6 | 61.4 | T | 61.5 | 20 | 22 | 21½ |
| 10 | 19.8 | 62.1 | T½ | 62 | 20 | 23 | 21¾ |
| 10¼ | 20.0 | 62.7 | U | 62.5 | 21 | 23 | 22¼ |
| 10½ | 20.2 | 63.4 | U½ | 63 | 22 | 24 | 22¾ |
| 10¾ | 20.4 | 64.0 | V | 64 | — | 24 | — |
| 11 | 20.6 | 64.6 | V½ | 64.5 | 23 | 25 | 25 |
| 11¼ | 20.8 | 65.3 | W | 65 | 24 | 25 | 25 |
| 11½ | 21.0 | 65.9 | W½ | 66 | 24 | 26 | — |
| 11¾ | 21.2 | 66.6 | X | 66.5 | 25 | 27.75 | 27½ |
| 12 | 21.4 | 67.2 | X½ | 67 | 25 | 27.75 | 27½ |
| 12¼ | 21.6 | 67.9 | Y | 67.5 | 26 | 28.75 | 28¼ |
| 12½ | 21.8 | 68.5 | Z | 68 | 26 | 28.75 | 28¾ |
| 12¾ | 22.0 | 69.1 | Z½ | 69 | 27 | 28.75 | 29 |
| 13 | 22.2 | 69.7 | Z+1 | 70 | 27 | 30 | 29¼ |
“—” indicates no standard equivalent is commonly used in that region for this size.
Important Notes
- US, Canada, and Mexico use the numeric system shown above (3–13, including quarter sizes).
- UK, Australia, Ireland, New Zealand, and South Africa use the letter system (F–Z+1, including half sizes).
- Europe uses the ISO circumference in millimeters (44–70).
- Japan and Hong Kong use separate numeric systems that are close but not identical.
- Ring sizing can vary slightly between brands due to manufacturing tolerances. For the most accurate fit, we recommend visiting a local jeweler to confirm your size.
Need help?
Contact our customer care team at service@luceraro.com — we’re happy to assist you in finding the perfect fit.