Ring sizes: US, UK and EU

A US size is a number, usually from 3 to 13, in half and quarter steps; each full size adds about 0.8 mm to the inside diameter. A UK size is a letter, from about F to Z, with half sizes between. An EU size is the inside circumference in millimeters, so a 54 is a ring that is 54 mm around on the inside, which is a US 7 or a UK N½.

Sara converts any of them. Tell her the size you know and she designs to it; the table on the ring size guide shows every half size side by side.

Knowing your size in one system is enough. The EU system is the most exact because it is a measurement rather than a label, which is why Sara works in millimeters in CAD and converts to US or UK for you.

UK letters are approximate equivalents, not exact: a UK N½ and a US 7 differ by a fraction of a millimeter. Fingers also change size through the day and the year, and a wide band fits tighter than a thin one. None of this matters once Sara has a measurement and knows the band width.

Anyone ordering from outside the US, anyone who knows their size from a ring bought elsewhere, and anyone measuring at home for a surprise.

US 5 is about UK J½ and EU 49.3; US 6 is about UK L½ and EU 51.9; US 7 is about UK N½ and EU 54.4; US 8 is about UK P½ and EU 57.0. The full table runs from US 3 to 13.5 on the ring size guide, with inside diameters in millimeters.

To measure at home: the inside diameter of a ring that fits, a strip of paper around the finger for the circumference, or a plastic sizer, which is the most reliable. Measure in the evening, and if you are between sizes, go up.

Size changes the amount of metal in a band, so a larger size weighs and costs a little more, and a wide band more so. A first resize on a custom ring is covered; later resizes are priced on the repairs and services page.

Fingers change. If a ring starts to feel tight or loose after a few years, a resize is routine for a plain or half-eternity band; full eternity and some pavé bands have limits that Sara explains before you order.