What ring size am I?

How to measure your finger

Wrap a (non-stretchy) thread or paper strip around the base of the finger, mark where it overlaps and measure the length in mm with a ruler: that's the circumference. Alternatively measure the inner diameter of a ring that already fits well, ruler across the widest part.

How sizes work

The Italian (and French) size is simply the circumference in millimeters minus 40: a 54 mm finger wears size 14. US and UK sizes use different scales: the conversion is indicative, for important purchases get measured at a jeweler.

Tip

Measure at the end of the day (fingers swell slightly) and not when cold. Wide bands may need an extra half size.

Why the same size has three numbers

The three scales answer the same question in three ways: the Italian and French start from the circumference in millimetres and subtract 40 (or 39, depending on the jeweller), the American uses a conventional scale of whole and half numbers, the British uses letters. There is no exact conversion between them, only correspondence tables.

It is why a size bought online can arrive half a point out: manufacturers round differently and some start from 39 rather than 40. If the ring matters, the size should be taken by whoever will sell it, with their own sizing rings.

A finger changes through the day

Fingers swell with heat, salt, exercise and the evening, and shrink in the cold and in the morning. Between a measurement taken at eight on a winter morning and one taken at eight on a summer evening there can be a full half size.

The practical rule is to measure at the end of the day at a normal temperature, and to repeat the measurement at three different moments keeping the largest. A slightly loose ring can be worn, a tight one cannot: when in doubt always take the larger size.

A wide band goes one size up

A ring more than six millimetres tall covers more of the joint and rests on a part of the finger that tapers less: it goes on harder and grips more at the same nominal size. For wide wedding bands and band rings you go half a size up.

The knuckle counts too: if it is much thicker than the base of the finger, the ring has to pass the knuckle and will then sit loose. In that case the measurement is taken at the knuckle and the jeweller is asked for an internal sizer, which is the classic reversible solution.

Nearby tools

For the other sizes people get wrong when buying online there is Clothing size converter. If you are preparing a gift for an important date, Wedding anniversaries says which milestone it is.