Sizing in secret
Finding the size without asking
If the question is meant to be a surprise, the obvious method is out. Here are four that work, in order of how much you can rely on them, and what to do if none of them is possible.
One. Borrow a ring they already wear
The most reliable of the four. Take a ring they wear on the correct finger — the ring finger of the left hand, in most British households, though it is worth checking rather than assuming — and either bring it to be measured or lay it over the printed circles on the measuring guide.
Two cautions. A ring worn on a different finger tells you about that finger and nothing else; the ring finger and the middle finger commonly differ by two or three sizes. And a wide band needs a slightly larger size than a narrow one on the same hand, so a chunky signet is not a good reference for a 2 mm court band.
Take the ring in the evening and put it back before morning. Someone who wears a ring daily notices its absence quickly.
Two. Ask someone who is allowed to know
A sibling, a close friend, a parent. Often one of them already knows, or can find out over a lunch without it looking like anything. This is the method with the least risk of a wrong number and the most risk of the surprise leaking, so pick the person carefully.
If you go this way, ask them for the size and which finger it was measured on. A size with no finger attached to it is not much use.
Three. Measure while they sleep
Works, with a light touch. A length of non-stretch thread or a thin strip of paper wrapped once around the base of the finger, marked where it meets, then measured flat against a ruler in millimetres. Look the figure up in the circumference column of the size table.
Two problems to be aware of. Fingers are at their smallest during the night, so a reading taken at three in the morning can be half a size under. And the strip has to pass the knuckle, which you cannot check on a sleeping hand. Treat this as an estimate and round up.
Four. Order the sizer set and use it on a ring, not a finger
The steel sizer set is a fan of fixed bands, one per UK size. Slip them over a ring they already own until one matches the inside diameter. It takes a minute, it does not involve their hand at all, and it gives you a letter rather than a guess.
The set is GBP £15 and the full cost comes off your ring order afterwards, so in practice it costs nothing.
If you genuinely have to guess
It happens. In that case: go up, not down. A ring slightly too large can be worn on the day and brought in afterwards. A ring too small cannot be worn at all, which is a poor start to the evening.
The most common British women’s size is around L to N, and the most common men’s is around T to V. Those are averages across a whole population and they are not a substitute for a measurement, but if you are choosing between L and N with nothing else to go on, N is the safer error.
One exception to all of the above
None of this applies to a full eternity ring, which cannot be resized by any amount afterwards. Do not buy one on an estimate. If a full eternity band is what you want and the size is not certain, buy the sizer first — or choose a half eternity, which can be moved about a size. Resizing policy
After the question has been asked
If the ring turns out to be the wrong size and it is one that can be altered, the first resize within its stated window is free for twelve months. If you would rather start again, a stock-size ring can be sent back unworn within 14 days under the right to cancel.
What we cannot do is alter a ring beyond its window or resize one that has none. That is why the window is printed on every product page rather than buried in a policy.