The most reliable way to size a US finger for a bespoke ring made abroad is to visit a local jeweller, have the finger measured on a ring sizer, and share both the US size and the inside measurement in millimetres. With an accurate measurement, a ring made in the UK can fit just as well as one made locally.
In short: get measured professionally, share the size in millimetres as well as US numbers, and measure at the end of a normal day.
Why millimetres help
US ring sizes use numbers and quarter sizes, while the UK uses letters and half sizes. Converting between them is straightforward, but rounding can creep in. Sharing the inside diameter or circumference in millimetres removes any doubt. Our guide to US to UK ring sizes sets out the conversions.
Getting measured locally
Most jewellers in the US will measure a finger, often without charge. Ask them to use a set of sizing rings rather than a paper strip, and to measure the width you plan to wear, as wide bands fit more snugly than slim ones. Ask for the size in US numbers and in millimetres.
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When to measure
Fingers change through the day and with temperature. Measure at the end of a normal day, at room temperature, not straight after exercise or in the cold. If you can, measure twice on different days and compare.
Measuring at home
If you cannot visit a jeweller, a plastic ring sizer can be posted to you, and our ring sizing page explains how to use one. Avoid string or paper, which can stretch or slip. If you are sizing a surprise, an existing ring worn on the same finger can be measured instead.
Knuckles and fit
If your knuckle is larger than the base of your finger, a ring that slides over the knuckle may spin. A jeweller can suggest a slightly shaped band or sizing beads. Mention this when you share your size.
Working with a maker abroad
Send your size, the width you want and any notes about your knuckles. Ask the maker to confirm the size in writing before production. Our page on commissioning your ring remotely explains each step.
If the size is not quite right
Most plain bands can be resized later, though eternity bands and some designs are harder to adjust. Ask about resizing before you order, so you know what to expect.
Everyday care
Clean the ring gently at home with warm water, a drop of mild washing up liquid and a soft brush, then dry it with a lint free cloth. Take it off for the gym, heavy lifting, gardening and swimming. Have the claws checked by a jeweller about once a year, and add the ring to your insurance as soon as you have it, checking that cover applies when you travel.
If you notice a loose stone, a bent claw or a ring catching on clothing, stop wearing it and take it to a jeweller promptly. Small repairs are simple when caught early, and a regular check helps the ring last for generations.
Wide bands and comfort fit
A wide band covers more of the finger and usually needs a slightly larger size than a slim band. A comfort fit band, rounded on the inside, can feel looser than a flat one of the same size. Tell your maker the width and profile you want, so they can allow for it.
Sizing for a surprise
If the ring is a surprise, borrow a ring your partner already wears on the same finger and ask a jeweller to measure it on a mandrel. Note whether it fits snugly or loosely. A ring worn on another finger is a rough guide only.
Frequently asked questions
How do I measure my ring size in the US for a ring made in the UK?
Visit a local jeweller, get measured on sizing rings, and share both the US size and the measurement in millimetres.
Is a US ring size the same as a UK size?
No. The US uses numbers and the UK uses letters, so a conversion is needed.
When is the best time to measure my finger?
At the end of a normal day, at room temperature.