Getting the size right is the one part of buying a wedding ring that people routinely get wrong, and it is the only part that cannot be fixed by choosing a nicer design. A beautiful ring in the wrong size does not get worn.

The good news is that measuring properly is not difficult. It just needs doing at the right time of day, in the right conditions, and with the right method for the ring you are buying.

How UK ring sizes work

Britain uses letters, from about A at the smallest to Z and beyond, usually with half sizes marked as “K½” or “K and a half”. Each letter step is a little over 1.2mm of internal circumference, which is small enough that one size can genuinely be the difference between comfortable and irritating.

Two measurements sit underneath the letter, and these are the ones that actually matter because they never vary between countries:

• Inside circumference — the distance all the way round the inside of the ring, in millimetres.
• Inside diameter — the width straight across the inside.

If you ever order from abroad, or compare charts that disagree, work in millimetres rather than letters or numbers.

UK size	Inside circumference (mm)	Inside diameter (mm)
H	45.4	14.5
I	46.7	14.9
J	48.0	15.3
K	49.3	15.7
L	50.6	16.1
M	51.9	16.5
N	53.1	16.9
O	54.4	17.3
P	55.7	17.7
Q	57.0	18.2
R	58.3	18.5
S	59.5	19.0
T	60.8	19.4
U	62.1	19.8
V	63.4	20.2
W	64.6	20.6

Figures are rounded to one decimal place. Different charts round differently, so a variation of a tenth of a millimetre between sources is normal.

The most accurate method: a professional measure

A jeweller uses a set of steel sizing rings and slides them onto your finger until one fits properly. This is more accurate than anything you can do at home, because a real ring behaves differently from string or paper, and because an experienced person can feel whether it will pass the knuckle correctly.

It takes two minutes and is normally free. If you are anywhere near a jeweller, do this.

Measuring at home

If you are buying online or measuring in secret, there are three home methods. They are listed here best first.

1. A plastic ring sizer

A thin plastic belt that you thread into a loop and tighten on your finger, marked with sizes. These are cheap, and they are by far the most reliable home method because they mimic a real ring.

The important bit: do not just tighten it until it feels snug. Pull it right off over the knuckle and back on again a few times. If it will not come off comfortably, it is too small, however good it feels at the base.

2. Measure an existing ring

If you already own a ring that fits the correct finger, this is very accurate. Lay it on a ruler and measure the inside diameter straight across, in millimetres, then find that figure in the chart above.

Two warnings. Measure the inside, not the outside. And make sure it is a ring worn on the same finger of the same hand, because your two hands are not the same size.

3. String or paper (use only as a last resort)

Wrap a strip of paper or a piece of non-stretchy string round the base of the finger, mark where it overlaps, lay it flat and measure the length in millimetres. That length is the circumference, so read it against the middle column of the chart.

This method is the least reliable, because paper flattens the skin and string stretches, and because it measures the base of the finger without accounting for the knuckle. Expect it to come out small. It is fine for getting into the right area, not for a final order.

The mistakes that ruin a home measurement

• Measuring when cold. Fingers shrink noticeably in cold weather and first thing in the morning. Measure in a warm room, later in the day.
• Measuring at the end of a very hot day, or after salty food or alcohol. Fingers can swell. Aim for a normal evening, not an extreme.
• Ignoring the knuckle. If your knuckle is much larger than the base of your finger, you need a size that passes the knuckle, and then a fitted sizing bar inside the ring to stop it spinning. Sizing to the base alone means the ring will never go on.
• Forgetting band width. A wide band feels tighter than a narrow one at the same size. As a working rule in the trade rather than a measured figure, allow up to half a size larger for bands of about 6mm and above.
• Using the wrong hand. Your dominant hand is usually very slightly larger.
• Measuring once. Measure on three different days and take the most common answer.

Measuring in secret for a proposal

If you are buying an engagement ring without them knowing, the reliable options are:

• Borrow a ring they already wear on the correct finger and have it measured, or press it into a bar of soap to take an impression.
• Ask someone close to them who wears a similar size to try on rings on their behalf.
• Buy a size that is likely to be close and have it adjusted afterwards. Most jewellers, including us, will resize a plain or partly set ring after purchase.

If you take the third route, avoid a full eternity design at that stage, because full eternity bands usually cannot be resized at all. Something like our Solitaire Round Cut Engagement Ring is far more forgiving, as there is plenty of plain metal at the back of the shank to work with. Prices correct at the time of writing.

Which rings can be resized, and which cannot

Ring type	Resizable?
Plain band	Yes, up or down, within reason
Half or three-quarter eternity band	Usually yes, using the plain section at the back
Full eternity band	Normally no. Diamonds run the whole way round, so there is nothing to cut into
Solitaire or halo engagement ring	Usually yes, though pavé stones near the join need care
Very wide or very heavy band	Possible but harder, and there is a limit to how far it can move

This matters at the point of purchase, not afterwards. If you love the look of a full eternity ring but are not confident about the size, a three-quarter version such as our Stackable Round Cut Three Quarter Eternity Band looks the same from the front and keeps your options open. A simple Minimalist Round Cut Wedding Band is the most adjustable of all.

When to measure before a wedding

Measure early to place the order, then check the fit again about a week before the day. Weight change, training, warm weather and the general stress of a wedding can all move a size. Finding a problem a week out gives a workshop time to act. Finding it on the morning does not.

Frequently asked questions

How do I find my wedding ring size at home?

The most reliable home method is a cheap plastic ring sizer, pulled on and off over the knuckle several times. Measuring the inside diameter of a ring you already wear on the same finger is nearly as good. String and paper are the least accurate and usually read small.

What time of day should I measure my finger?

Late afternoon or evening, in a warm room. Fingers are at their smallest first thing in the morning and in cold weather, which is exactly when a measurement will mislead you.

Should a wedding ring be tight or loose?

It should need a little effort to pass the knuckle, then sit comfortably without sliding freely round the finger. If it comes off without resistance it is too big. If it needs soap to remove, it is too small.

Does the width of the band change the size I need?

Yes. Wider bands cover more of the finger and feel tighter, so a wide band often needs up to half a size more than a narrow one. That is a rule of thumb in the trade rather than a fixed measurement, so try a wide sizer if you can.

What if my knuckle is much bigger than my finger?

Size the ring so it passes the knuckle, then have a jeweller fit a small sizing bar or beads inside the shank. That stops the ring spinning at the base without making it impossible to put on.

When you are ready

Get the size right and everything else becomes a pleasure rather than a worry. Browse the wedding ring collection or the engagement rings when you know your measurement.

Every ring is hand-made to order in solid gold or platinum with lab-grown diamonds and a free IGI certificate on the centre stone, and comes with free insured UK delivery and 30-day returns. If you need a size outside our standard range, or you are not sure which size to order, get in touch before you buy and we will help. Bespoke designs are made at no extra design cost.