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International · Instant · Free
Ring Size Converter
Convert any ring size instantly between US, UK, EU, France, Germany, Switzerland, Japan and Brazil — plus millimetres and inches.
Instant Converter
Change any field — the rest update automatically.
Inside circumference, mm
Inside
Inside
Inside
Inside
Matched inside diameter 17.30 mm · circumference 54.35 mm
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International Ring Size Chart
A complete side-by-side reference for the world's most common sizing systems.
| US | UK | EU | FR | DE | CH | JP | BR | Ø mm | Ø in | Circ. mm |
|---|---|---|---|---|---|---|---|---|---|---|
| 3 | F | 44 | 44 | 14 | 4 | 4 | 7 | 14.00 | 0.551 | 43.98 |
| 3.5 | G | 45 | 45.5 | 14.5 | 5.75 | 5 | 8 | 14.40 | 0.567 | 45.24 |
| 4 | H | 47 | 46.75 | 14.75 | 7 | 7 | 9 | 14.80 | 0.583 | 46.50 |
| 4.5 | I | 48 | 48 | 15.25 | 8.25 | 8 | 10 | 15.20 | 0.598 | 47.75 |
| 5 | J½ | 49 | 49.25 | 15.75 | 9.5 | 9 | 11 | 15.60 | 0.614 | 49.01 |
| 5.5 | K½ | 50 | 50.5 | 16 | 10.75 | 10 | 12 | 16.00 | 0.630 | 50.27 |
| 6 | L½ | 52 | 51.75 | 16.5 | 12 | 12 | 13 | 16.45 | 0.648 | 51.68 |
| 6.5 | M½ | 53 | 53 | 17 | 13.25 | 13 | 14 | 16.90 | 0.665 | 53.09 |
| 7 | N½ | 54 | 54.25 | 17.25 | 14.5 | 14 | 15 | 17.30 | 0.681 | 54.35 |
| 7.5 | O½ | 56 | 55.5 | 17.75 | 15.75 | 15 | 16 | 17.70 | 0.697 | 55.61 |
| 8 | P½ | 57 | 56.75 | 18.25 | 17 | 16 | 17 | 18.10 | 0.713 | 56.86 |
| 8.5 | Q½ | 58 | 58 | 18.5 | 18.25 | 17 | 18 | 18.50 | 0.728 | 58.12 |
| 9 | R½ | 59 | 59 | 19 | 19.5 | 18 | 19 | 19.00 | 0.748 | 59.69 |
| 9.5 | S½ | 61 | 60.25 | 19.5 | 20.75 | 19 | 20 | 19.40 | 0.764 | 60.95 |
| 10 | T½ | 62 | 61.5 | 19.75 | 22 | 20 | 21 | 19.80 | 0.780 | 62.20 |
| 10.5 | U½ | 63 | 62.75 | 20.25 | 23.25 | 22 | 22 | 20.20 | 0.795 | 63.46 |
| 11 | V½ | 65 | 64 | 20.75 | 24.5 | 23 | 23 | 20.60 | 0.811 | 64.72 |
| 11.5 | W½ | 66 | 65.25 | 21 | 25.75 | 24 | 24 | 21.00 | 0.827 | 65.97 |
| 12 | X½ | 67 | 66.5 | 21.5 | 27 | 25 | 25 | 21.40 | 0.843 | 67.23 |
| 12.5 | Z | 68 | 67.75 | 22 | 28.25 | 26 | 26 | 21.80 | 0.858 | 68.49 |
| 13 | Z+1 | 70 | 69 | 22.25 | 29.5 | 27 | 27 | 22.20 | 0.874 | 69.74 |
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How to measure your ring size
Five steps and a piece of string is all it takes to get a jeweler-accurate reading.
- Step 1
Wrap
Wrap a piece of string or thin strip of paper snugly around the base of your finger.
- Step 2
Mark
Mark the exact point where the two ends of the string meet.
- Step 3
Measure
Lay the string flat and measure the length with a ruler in millimetres.
- Step 4
Divide
Divide the circumference by π (3.14159) to get the inside diameter.
- Step 5
Convert
Enter the value into the converter above to find your international size.
Prefer paper? Get the printable ring size chart
A free 1:1 scale PDF with true-to-life sizer circles, a cut-out finger strip and the full international conversion table.
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Frequently asked questions
Everything jewelers get asked about ring sizing — answered.
How do I measure my ring size?
Wrap a piece of string or thin paper around the base of your finger, mark where it meets, and measure that length in millimetres. Divide by π (3.14159) to get the inside diameter, then use the converter above.
What if I'm between sizes?
Always choose the larger size. Rings can be sized down more easily than up, and fingers swell throughout the day and in warm weather.
Are UK and US ring sizes different?
Yes. The UK uses a letter-based system (A–Z, sometimes with ½ steps), while the US uses numeric sizes. A UK size N½ is roughly a US size 7.
Can finger size change?
Yes. Fingers swell with heat, exercise, salt intake and pregnancy, and shrink in cold weather. Weight changes and age also affect ring size, so remeasure every few years.
How do I secretly measure someone's ring?
Borrow a ring they already wear on the target finger and trace the inside on paper, or press it into soap. Measure the inside diameter and enter it into the converter to get their international size.
Which countries use letter-based ring sizes?
The United Kingdom, Ireland, Australia and New Zealand use letter sizes (A through Z, with ½ increments).
Which countries use number-based ring sizes?
The United States, Canada, Mexico, Japan and most of continental Europe (France, Germany, Switzerland, Italy) use numeric sizes, though the scales differ.
Ring sizing guides
Original, in-depth articles on measuring, fit, metals, resizing and buying rings abroad.
Ring Sizing Tools Compared: Mandrels, Sizers and Printables
Which sizing tool to trust, from professional steel mandrels to plastic multisizers and printable paper charts.
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A Short History of Ring Sizing
How ring measurement evolved from local guesswork to national standards, and why the world still has no single system.
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Five Signs Your Ring Does Not Fit Properly
How to tell whether a ring is genuinely the wrong size or just needs adjusting, and what each symptom means.
4 min read
Ring Sizes for Children and Teenagers
Typical children's ring sizes by age, how quickly fingers grow, and how to buy a ring a child can wear for more than one season.
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Stacking a Wedding Band With an Engagement Ring
How to size and choose a wedding band that sits flush against an engagement ring without rubbing, gapping or feeling tight.
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