Stuck between two ring sizes

You measured carefully and the answer came out halfway between two sizes. That is the usual outcome, not a mistake — here is how to choose.

Published 2026-10-23

Ring sizes are a grid laid over something continuous. Fingers come in every width there is; shops stock half sizes. The step between two of them is 1.28 mm of circumference — about the thickness of two credit cards — so a finger that lands exactly on a stocked size is the exception.

The short answer: go up

In almost every case, order the larger size. Four reasons, in order of how much they matter:

1. A tight ring is the one that stops being worn. It has to come off with soap, it marks the finger, and on a hot day or a long flight it does not come off at all. A slightly loose ring is a minor annoyance.
2. Sizing down is cheaper and cleaner than sizing up. Taking metal out and rejoining a band is routine. Stretching a ring thins the wall and distorts the shank, and going up more than a size usually means cutting it and adding metal — more work, and a visible join on some finishes.
3. Fingers grow. Over ten or twenty years most do, and arthritic knuckles need more clearance, not less.
4. The ring still has to pass the knuckle. The larger size gives you that margin.

When to go down instead

• The knuckle is much larger than the base of the finger. Then the ring will spin at the base whatever you do. Size it to pass the knuckle, but ask for sizing beads — two small bumps soldered inside the band — rather than compensating with a smaller ring you cannot get on.
• It is a comfort-fit band. The inside is domed rather than flat, so less of it touches the skin and it slides on more easily. Comfort-fit rings often run a quarter to a half size large; order the smaller of the two.
• You measured in the evening after a hot day, a salty meal or a flight. That reading is the top of your range, not the middle of it. Measure again on an ordinary morning and compare.
• It is a thin band, 2 mm or less, and you measured generously. Thin bands feel looser at the same size.

Band width changes the answer

This is the factor people miss. A wide band touches far more of the finger and cannot flex round the knuckle the way a thin one does, so it feels tighter at the same measured size. The trade allows for it:

The converter applies this for you once you set the band width.

How far apart the sizes really are

It helps to see the distances. A quarter size is 0.64 mm of circumference, a half is 1.28 mm, a whole is 2.55 mm. A British letter is 1.25 mm and a Japanese 号 is 1.05 mm — which is why a conversion between the two systems almost never lands on a whole number.

For comparison, the swing in your own finger between a cold morning and a hot evening is routinely 1–2 mm, and after a long-haul flight it can be more. Your finger moves across more than a whole size in a day. That is the real reason "between sizes" is normal: there is no single true size to be between.

If the ring cannot be resized

Some rings allow no second chance:

• Eternity bands set with stones all the way round cannot be cut without destroying the setting.
• Tension settings hold the stone by spring pressure in the shank. Changing the shank changes the pressure.
• Tungsten carbide and ceramic are too hard to work and will crack.
• Titanium can sometimes be sized by a specialist, usually not.
• Rings with an inlay, an engraved pattern all round, or a milgrain edge can be sized, but the pattern will not match at the join.

For any of those, go to a shop and have the finger measured on a steel mandrel, at the end of the day, with warm hands. Ask the jeweller to try the actual width of band you are buying — a good shop keeps wide sizers for exactly this.

Seasons, travel and other swings

Most people notice their rings are looser in winter and tighter in summer. Heat widens the blood vessels in the hands and cold narrows them, so a ring that is perfect in January can be half a size tight in July, and the reverse. If you measured at one extreme, allow for the other — and if you live somewhere with hot summers, lean towards the larger size.

Air travel, a salty meal, a long run and pregnancy all add fluid to the fingers for hours or for months. None of them is the right moment to size a ring that has to fit for years. Measure on an ordinary day, at an ordinary temperature, and then decide.

A practical routine

1. Measure three times across two days: once mid-morning, once in the evening, once the day after.
2. Throw away any reading taken with cold hands.
3. Take the largest of what is left as your working number.
4. Add for band width: a quarter from 4 mm, a half from 6 mm.
5. Round up to the nearest stocked size.
6. Check the shop will resize it once for free. Many will, and that turns the whole question into a small one.

What a jeweller will tell you

Ask any bench jeweller and you get the same answer: they would far rather make a ring smaller than bigger. Sizing down a plain band is a cut, a squeeze and a solder — twenty minutes and almost invisible. Sizing up by more than a size means adding a piece of metal, matching the colour, and polishing the join out, and on some alloys the seam will always be faintly visible under a loupe.

So when you are genuinely torn, remember that the larger ring keeps both options open and the smaller one does not.