How to Measure Ring Size at Home (UK Sizes Explained)

You don't need a jeweller to measure ring size accurately. If you have a piece of string, a ruler, and five quiet minutes, you can get within half a UK ring size of the right answer — which is well within the tolerance of any resize we'd do for you at no charge.

This guide covers the three methods we'd recommend, in order of accuracy. It also covers the surprise question that catches most couples out: whose finger are you measuring, and which one?

Before you start: three things that matter

1. Measure the right finger. Engagement rings traditionally go on the third finger of the left hand in the UK and Ireland (the "ring finger"). Wedding bands go on the same finger. Note: in some European countries the convention is the right hand instead — confirm with your partner if you're not sure.
2. Measure at the right time of day. Fingers swell in the morning, in warm weather, after exercise, after salty food, and when stressed. Measure at the end of the day, at room temperature, when relaxed. This gives the most accurate size for everyday wear.
3. Consider the band width. Wide bands (4mm+) fit tighter than thin bands at the same nominal size — if the ring style is wide, go up half a size.

Method 1 (most accurate): An existing ring

If your partner has a ring that fits a similar finger well, measure it. This is the most reliable home method because you're measuring a known-good fit.

What to do:

1. Find a ring your partner wears comfortably on the finger you're sizing.
2. Lay it flat on a ruler with millimetre markings.
3. Measure the internal diameter (across the inside of the ring) at the widest point, in millimetres.
4. Use the conversion table below.

This method is accurate to within roughly ¼ of a UK ring size if you measure carefully. A digital caliper is more accurate than a ruler, but a ruler is fine — round to the nearest 0.5mm.

Method 2: String and a ruler

If you don't have an existing ring to measure, this is the next-best method.

What to do:

1. Cut a piece of thin string about 100mm long. String or floss works better than a strip of paper.
2. Wrap it once around the base of the finger (where the ring will sit), snug but not tight. The skin should not indent.
3. Mark the point where the string meets itself.
4. Lay the string flat against a ruler. Measure the distance from the end to the mark, in millimetres. This is the finger circumference.
5. Use the table below.

Tip: measure three times. If you get three slightly different numbers, take the average — and if the variation is more than 2mm, you're wrapping too loose or too tight.

Method 3: Printable ring sizer

We can email you a free printable UK ring sizer that converts directly to UK sizes — message us on WhatsApp and ask for one. The PDF prints to a known size on standard A4 (you check by measuring the calibration bar), and you wrap it around the finger or thread it like a belt.

Printed sizers are accurate to within half a size if you print at 100% scale (not "fit to page") and verify the calibration bar with a ruler.

UK ring size conversion table

UK ring sizes go in alphabetical letters, with half sizes between (e.g. L½ between L and M). Half sizes correspond to roughly 0.6mm of finger circumference — meaningful enough to matter on a comfortable everyday ring.

What if I'm between sizes?

Always size up, not down. Here's why:

• A slightly loose ring is annoying — it spins or slides on the finger — but you can always wear it.
• A too-tight ring can't be worn at all, and getting it on or off causes finger swelling that makes the problem worse.
• We resize for free within 12 months on most styles.

The only exception: if your partner regularly works with hands in cold conditions (gardening, outdoor sports) where fingers shrink, size to the cold-finger size rather than up.

Special cases

Wide bands (4mm+): Size up a half. A 5mm wide band feels tighter than a 2mm band at the same nominal size because there's more contact area with the finger.

Knuckles bigger than base: Common, particularly as people get older or after pregnancy. The ring needs to clear the knuckle to go on but not be so loose at the base that it spins. The fix is usually a slightly larger ring with internal "sizing beads" — small bumps on the inside of the band that grip the base of the finger. We add these free of charge if needed; ask when ordering.

Cold or hot weather: Fingers can change by half a UK size between summer and winter for some people. If you're between sizes, size for the time of year your partner will wear the ring most.

Surprise proposals: If you can't measure your partner's finger directly without giving the game away, three workarounds: 1. Borrow a ring they wear on a similar finger, and bring it to us for sizing — we'll size from the ring and return it within 24 hours. 2. Ask a friend to compare hand size against a ring of known size. 3. Order a slightly-larger placeholder ring to use at the proposal, then come in together for the final sizing and the real ring. Many of our bespoke clients do this — there's no charge for resizing within 12 months.

How we resize a ring

If a ring is the wrong size, almost every Diamond Hub piece can be resized by 1–2 sizes up or down without affecting the design. The exceptions are full eternity bands, tension settings, and some intricate pavé designs where adding or removing metal would affect the stones.

The first resize is free within 12 months of purchase. After that, we charge a small fee that depends on the metal and complexity (typically £40–£90 for a standard resize, more for platinum or complex settings).

When in doubt, come in

We have ring sizing fans at both our Leicester and London showrooms — no appointment needed. We'll size your partner's finger accurately in two minutes. The sizing is free even if you don't buy.

Further reading

• The 4Cs of Diamonds Explained
• Engagement Ring Styles Explained