How to measure your ring size properly

A ring that is half a size out is not a small problem. Too tight and it will not pass the knuckle; too loose and it turns, wears unevenly, and eventually goes down a drain.

Time of day matters more than you would think

Fingers are smallest in the early morning and largest in the late afternoon. Heat swells them; cold shrinks them. Salt, exercise, alcohol and altitude all move the number, and the swing across a single day is commonly half a size.

Measure at the end of the day, in a warm room, when your hands are at rest. Size to the largest your finger reasonably gets, or you will own a ring you cannot wear in July.

The knuckle problem

A ring has to pass the knuckle and then sit on a narrower base. If your knuckle is much larger, size to clear the knuckle — a ring that spins slightly is a nuisance; one you cannot get on is useless.

For a pronounced knuckle, ask about sizing beads: two small additions inside the band that hold the ring centred without preventing it going on.

Three ways to measure

Measure a ring you already own

The most reliable method, provided the ring fits the same finger on the same hand. Measure the inside diameter across the widest point. Our on-screen sizer lets you calibrate the display against a bank card and match the ring to a circle.

Measure your finger

Wrap a strip of paper around the base of the finger, snug but not tight. Mark the overlap, lay it flat, and measure to the mark in millimetres. That is the inner circumference — enter it in the sizer.

Use paper, not string. String stretches, and a stretched measurement produces a loose ring.

Come in

A set of steel sizing rings settles it in a minute, and for an engagement ring it is worth the trip.

Width changes fit

A wide band feels tighter than a narrow one of the same nominal size, because it grips more of the finger. For anything above about 6mm, go up a quarter to a half size.

Buying a surprise

Borrow a ring she already wears on the right finger and have it measured — far better than guessing. Failing that, details to follow average sizes are around details to follow for women and details to follow for men, but treat that as a starting point, not an answer.

If it is wrong, we will resize it. details to follow Note that full eternity rings and stone-set-all-round designs generally cannot be resized at all — worth knowing before you choose one as a surprise.

Common mistakes

• Measuring cold hands first thing in the morning.
• Using string instead of paper.
• Measuring the outside of an existing ring rather than the inside.
• Sizing a wide band as though it were narrow.
• Measuring a different finger, or the same finger on the other hand — the dominant hand is usually slightly larger.