Convert your ring size across major international sizing systems. Enter your US/Canada size or ring diameter in millimeters, and get the equivalent sizes for UK/Australia, France, Germany, Japan, and Switzerland — all in one place.
Ring Diameter (mm)
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US / Canada Size
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UK / Australia Size
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France Size
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Germany Size
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Japan Size
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Switzerland Size
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Select your known measurement system from the dropdown (e.g., US/Canada or Diameter in mm), enter your size, and the converter will instantly show the equivalent sizes for all other international systems. The full conversion table below also lets you browse all sizes at a glance.
Yes. The US and Canada use a numeric scale starting near size 3. The UK and Australia use alphabetical letters (e.g., N, O, P). France and Switzerland use the inner circumference in millimeters, Germany uses inner diameter in millimeters, and Japan uses a numeric scale that differs from the US system. Always verify which standard a jeweler uses before ordering.
Ring sizing systems themselves are gender-neutral — the same scale applies to everyone. However, average ring sizes differ: women typically wear sizes 5–7 (US) and men typically wear sizes 9–12 (US). When shopping, ring styles may be labeled for a gender, but the size numbers work the same way.
The most reliable DIY method is wrapping a thin strip of paper or string around your finger, marking where it overlaps, and measuring the length in millimeters — that gives your inner circumference. Divide by π (3.1416) to get your diameter. You can then use that diameter in this converter to find your size in any system.
A ring should slide over your knuckle with slight resistance and sit snugly at the base of your finger without spinning freely. If you're between sizes, going a half-size up is generally recommended, especially for wider bands which tend to fit tighter than narrow ones.
Yes. Wider bands sit higher on the finger and can feel tighter, so jewelers often recommend sizing up by a half to full size for bands wider than 6mm. Narrow bands (under 4mm) tend to fit more like the measured size. Always mention band width when asking a jeweler for sizing advice.
Yes, finger size can change due to weight fluctuations, pregnancy, aging, temperature, and time of day. Fingers are typically slightly larger in the evening and when warm. For the most consistent measurement, size your finger at the end of the day when it's at its largest.
Most reputable jewelers offer a one-time free resizing or an exchange within a set period. Check the retailer's sizing policy before purchasing. Rings with stones set around the full band (eternity rings) or made from certain metals like titanium or tungsten may be difficult or impossible to resize.