Ring sizes can be confusing. If in doubt, here is a chart to help you figure out your approximate size. I find it easiest to measure the circumference of your preferred finger (which equals to the Internal Circumference of the ring), and find your UK size equivalent from there.

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From what I could find out, the EU standard is simply the internal circumference rounded up or down to half-numbers. If this doesn’t help, any jeweller will size your fingers for free.