Ring Size Converter

Why UK sizing runs on letters

British ring sizing has kept its own letter scale, from A up to Z with half sizes marked as a plus, rather than adopting the millimetre-based numbering used across continental Europe. Many UK jewellers keep an in-store set of sizing rings lettered this way, so quoting a letter such as L or N is understood immediately on the high street, even though the same finger measured in Germany or France would simply be read off in millimetres.

Size chart by system

The table above converts a measured circumference, or the inner diameter of a ring that already fits, into the UK letter, the US numeric size, and the EU value, which is the circumference in millimetres used on the continent. Working from a physical measurement rather than a size already known elsewhere avoids the guesswork of matching a foreign label to a UK letter by memory.

Measuring at the right time of day

A finger swells a little with warmth and activity and shrinks slightly in the cold, so a ring bought from a measurement taken first thing in the morning can end up loose by the evening. Fitting rooms and independent jewellers in the UK commonly advise measuring later in the day, when the finger sits closer to its largest, particularly before ordering a ring online that cannot easily be resized.

Limits of this converter

A wide band needs noticeably more room than a thin one to pass over the knuckle comfortably, and this chart does not account for band width or metal thickness. The figures follow a commonly published size chart and give an indicative equivalence, not a promise of fit, so a proper fitting at a jeweller remains the safer route before an expensive or engraved purchase.