Free ring size converter tool. Convert between US, UK, EU, Japanese, and metric (mm) ring sizing systems. Includes full reference chart and home measuring instructions.
- Converts between US, UK, EU, Japanese, and millimeter systems
- Full size chart with all standard sizes
- Includes home measuring guide (string and paper strip methods)
- Wider bands typically need half size up
- Free to use, no signup required
Free tool
Ring Size Converter
Convert between US, UK, European, Japanese, and metric ring sizes instantly. Includes a full reference chart and instructions for measuring at home.
Reference chart
| US | UK | EU | JP | mm ⌀ |
|---|---|---|---|---|
| 1 | B | 41 | 1 | 12.95 |
| 1.5 | C | 42 | 2 | 13.26 |
| 2 | D | 42.5 | 3 | 13.56 |
| 2.5 | E | 43.5 | 4 | 13.87 |
| 3 | F | 44 | 5 | 14.17 |
| 3.5 | G | 45 | 6 | 14.48 |
| 4 | H | 46 | 7 | 14.78 |
| 4.5 | I | 47 | 8 | 15.09 |
| 5 | J | 48 | 9 | 15.40 |
| 5.5 | K | 49 | 10 | 15.70 |
| 6 | L | 50 | 11 | 16.01 |
| 6.5 | M | 51 | 12 | 16.31 |
| 7 | N | 52 | 13 | 16.62 |
| 7.5 | O | 53 | 14 | 16.92 |
| 8 | P | 54 | 15 | 17.23 |
| 8.5 | Q | 55 | 16 | 17.53 |
| 9 | R | 56 | 17 | 17.84 |
| 9.5 | S | 57 | 18 | 18.14 |
| 10 | T | 58 | 19 | 18.45 |
| 10.5 | U | 59 | 20 | 18.76 |
| 11 | V | 60 | 21 | 19.06 |
| 11.5 | W | 61 | 22 | 19.37 |
| 12 | X | 62 | 23 | 19.68 |
| 12.5 | Y | 63 | 24 | 19.98 |
| 13 | Z | 64 | 25 | 20.29 |
| 13.5 | Z+1 | 65 | 26 | 20.60 |
| 14 | Z+2 | 66 | 27 | 20.90 |
| 14.5 | Z+3 | 67 | 28 | 21.21 |
| 15 | Z+4 | 68 | 29 | 21.51 |
| 15.5 | Z+5 | 69 | 30 | 21.82 |
| 16 | Z+6 | 70 | 31 | 22.12 |
How to measure your ring size at home
- Cut a thin strip of paper or use a piece of string, about 10 cm long.
- Wrap it snugly around the base of the finger you want to measure.
- Mark where the strip overlaps, then lay it flat and measure the length in millimeters.
- Enter the circumference above and select "Circumference (mm)" as the system.
Tip: Measure at the end of the day when fingers are slightly larger. Avoid measuring when very cold or very hot.
About this tool
Ring sizes vary significantly across countries. The US and Canada use a numeric system (1–16 with half sizes), the UK and Australia use letters (A–Z+), Europe uses circumference in millimeters, and Japan uses its own numeric scale.
This converter maps all major systems using standardized diameter and circumference measurements. Note that there are minor variations between standards, and ring width can affect the perceived fit. Wider bands typically require a half size up.
Common questions
Wrap a strip of paper or string around the base of your finger, mark where it overlaps, then measure the length in millimeters. That gives you the circumference. Use this converter to find your size in any system. For best results, measure in the evening when fingers are slightly larger.
Yes. Wider bands (over 6mm) fit tighter because more metal contacts your finger. Most jewelers recommend going up half a size for bands 6-8mm wide, and a full size up for bands over 8mm.
Yes. The US and Canada use the same numeric ring size system. Sizes run from 1 to 16 with half and quarter sizes. The most common men's sizes are 9-11 and women's sizes are 5-7.
UK ring sizes use letters (A through Z+) while US uses numbers. They don't map one-to-one. For example, UK size L equals US size 6, and UK size T equals US size 10. This converter handles the exact mapping for every size.
Yes. Fingers swell in heat and shrink in cold. A ring that fits perfectly in summer may feel loose in winter. If you're between sizes, most jewelers recommend sizing for warmer conditions since a slightly loose ring is easier to fix than one that's stuck.
Related resources
Save your results. Get our free pricing guide
Download our complete ring sizing reference with printable size strips included.