Compare US, UK, EU, Japanese, Swiss and millimeter inner-diameter sizes. Results update automatically from the Cartier international ring-size chart; they are a reference for cross-system comparison, not a guarantee for every product.
Use a known size or measured inner diameter to narrow a seller’s size range before checking that brand’s chart and trying the ring on.
US, EU, JP, CH and mm accept finite numbers. UK accepts a letter and optional half size, such as L 1/2. EU denotes circumference in millimeters; mm denotes inner diameter. JP means Japan only.
Supported ranges are US 3–13.25, EU 44–71, JP 4–31, CH 4–31 and approximately 14.01–22.60 mm diameter. The UK chart runs from F 1/2 to Z 1/2. Invalid and out-of-range inputs clear the result and show an explanation.
The converter uses circumference as its internal unit. US and UK values between chart entries are linearly interpolated; UK output rounds to the nearest half size. EU equals circumference, the chart’s Japanese number and Swiss number equal circumference minus 40, and diameter = circumference / π. Missing UK entries at the upper end display “—”.
This chart gives EU 52, about 16.55 mm inner diameter and UK L 1/2. Tiffany’s measurement guide rounds US 6 to 16.5 mm. Small chart differences are expected.
Use L, L 1/2 or L½. Additional text and quarter-letter sizes are rejected; UK output rounds to the nearest half size.
No. JP denotes Japan in the cited chart. Chinese and brand-specific sizing systems are not independently modeled.
Sizes must fit the chart range of 44–71mm circumference. The converter does not extrapolate beyond it.
Convert ring sizes between different international standards.