Find your ring size

A ring size can be read two ways. The circumference is the length of the thread that goes around the finger: between 52 and 70 millimetres on an adult. The inner diameter is the width of the ring seen face on: between 16 and 22 millimetres. Our rings run from size 6 to size 13; outside that range, write to us before ordering.

Both numbers are correct, and they measure two different things. A circumference is roughly three times the diameter. A 52-millimetre circumference looked up in a list of diameters lands on the highest value, and the ring ordered arrives three sizes too big.

On a ring, the diameter is always taken on the inside: from one inner edge to the other, through the centre. The outer edge gives a number one to two millimetres larger, which is worth one to three sizes.

The simple rule: a string gives you a circumference, a ruler laid on an existing ring gives you a diameter. Work out whether you have a circumference or a diameter first, and only then read the chart.

Cut a piece of string, thread, or a strip of paper about a centimetre wide. Wrap the strip around the base of the finger without pulling: the strip holds on the skin and can still turn.

Mark where the strip overlaps, then lay the strip flat and measure from the end to the mark. That gives you a circumference, in millimetres.

One detail decides the outcome: the ring has to clear the knuckle. If your knuckle is wider than the base of the finger, measure the knuckle too and keep the larger of the two.

The ruler method is the most reliable, and the most discreet. Take a ring that sits comfortably on the same finger, lay the ring on a ruler, and measure the inner diameter, from one inner edge to the other, through the centre.

Read that number in the diameter column of the chart below. Half a millimetre changes the size: measure twice, in daylight.

A finger swells with heat, exercise, salt and altitude, and shrinks in the cold and first thing in the morning. The gap can reach a full size between a finger measured on an empty stomach in January and the same finger on a summer evening after dinner.

Measure at the end of the day, at normal temperature, at rest and with warm hands. If two attempts give two different results, keep the larger one.

For a gift, asking for the size gives the surprise away. Three approaches work.

Quietly borrowing a ring they already wear, long enough to measure the ring with a ruler, remains the safest. Failing that, a ring can be set on a sheet of paper and its inner circle traced in pencil: the diameter can then be measured at leisure.

With no ring available, compare with your own fingers. A finger close to the size of your own gives a starting point, and you adjust one size up or down by eye. This estimate is approximate: when in doubt, take the size above.

A slightly loose ring is worn every day. When in doubt, take the size above.

A faulty ring is replaced. Replacement covers faults in operation, and the size is chosen once, when ordering.