How to measure ring size at home: UK letters, mm and botthms numbers

This is how to measure ring size at home in the UK. You do not need a jeweller. You need a ruler, five minutes and the chart below. This guide covers three methods, the conversion between UK letters, millimetres and our numbers, and the handful of rules that are specific to silicone. If you would rather have the maths done for you, the Fit Finder on our size guide measures a ring on your screen or a paper strip and tells you what to order.

Before you measure

• Measure at the end of the day. Fingers are larger in the evening, in heat and after exercise. A size taken first thing on a cold morning will be too small by teatime.
• Measure the finger you will wear it on. Left and right hands differ, sometimes by a full size.
• Check the knuckle. The ring has to get over it. If your knuckle is noticeably larger than the base of your finger, measure both and pick a size between them, closer to the base. Silicone stretches over a knuckle more forgivingly than metal, so you do not need to size up as much as you would for a metal ring.

Method 1: a ring you already wear

The most accurate home method, if you have a ring that fits the right finger.

1. Lay the ring flat on a ruler.
2. Measure the inside diameter, edge to edge, at the widest point, in mm. Be precise: half a millimetre is half a size.
3. Find that diameter in the chart below.

Method 2: a strip of paper

Good if you do not have a ring to hand.

1. Cut a strip of paper about 5 mm wide and 100 mm long. Do not use string; it stretches and gives a reading that is too large.
2. Wrap it round the base of the finger, snug but not tight, and mark where it overlaps.
3. Measure from the end to the mark. That is your circumference in mm.
4. Divide by 3.14 to get the diameter, then find it in the chart. Or put the circumference straight into the Fit Finder.

Do this twice and take the average. If the two readings differ by more than a millimetre, do it again.

Method 3: prediction

If you cannot measure (buying as a gift, for example), the Fit Finder can estimate a size from a few details, but a guess is a guess, which is why size swaps are quick and easy. If you are buying for someone else, borrow a ring they already wear on that finger if you can, and if not, pick your best guess and let them swap.

UK ring size chart: letters, mm and botthms numbers

Our rings use numbered sizes. The table maps each number to the inside diameter in mm and the nearest UK letter sizes.

• Size 4 — 14.9 mm — UK G to H (women's Flow only)
• Size 5 — 15.7 mm — UK J to K (women's)
• Size 6 — 16.5 mm — UK L to M (women's)
• Size 7 — 17.3 mm — UK N to O (women's and men's)
• Size 8 — 18.2 mm — UK P to Q (women's and men's)
• Size 9 — 18.95 mm — UK R to S (women's and men's)
• Size 10 — 19.8 mm — UK T to U (women's and men's)
• Size 11 — 20.6 mm — UK V to W (men's)
• Size 12 — 21.4 mm — UK X to Y (men's)
• Size 13 — 22.2 mm — UK Z (men's)
• Size 14 — 23.0 mm — UK Z+2 (men's)

Women's Active slim bands run sizes 5 to 10 and women's Flow rings 4 to 10. Men's Active bands run sizes 7 to 14. The numbers mean the same inside diameter in both ranges, so a size 8 women's and a size 8 men's fit the same finger; the difference is the width of the band.

The silicone rule: go down between sizes

This is the one thing people get wrong when they bring metal-ring habits to silicone.

Silicone has a little give. It stretches onto the finger and relaxes slightly over the first few days of wear. A ring that is exactly your measured size will feel comfortable on day one and loose by the end of the week. So:

• If your measurement lands between two sizes, order the smaller one.
• If your measurement lands exactly on a size, order that size, unless your finger is on the slim side with a small knuckle, in which case consider going down.
• If you lift weights or do a job where the ring gets pulled on a lot, go down. A snug ring stays put under a bar. A loose one rolls and catches.

Snug on day one is right. Comfortable on day one is too big.

Knuckle rule, properly

Measure the base of the finger (A) and the knuckle (B). If B is less than about 1 mm larger than A, order on A. If B is more than 1 mm larger, order the size between A and B, rounding toward A. Silicone will stretch over the knuckle and then settle at the base. Do not order on B alone; the ring will spin.

Width changes how a ring feels

A wider band sits on more skin, so it feels tighter than a narrow band of the same diameter. Our men's band is 8.7 mm wide; the women's Active slim band is 5.7 mm. If you are a woman choosing the men's width for a bolder look, or a man choosing the slim band, factor that in: wide feels half a size tighter, narrow feels half a size looser.

Use the Fit Finder

All of the above is built into the Fit Finder on the ring size guide. Place a ring on your screen or enter the length of a paper strip, tell it which band you are buying, and it returns your botthms size and UK letter with the rounding already applied. It takes less time than reading this paragraph.

If you get it wrong

You will not be the first. Wear the ring for a few days to let it settle, and if it is still wrong, swap it for another size within 30 days. Details on the returns page. Then pick your style from the men's or women's collection.

FAQ

Is a UK size N the same as a botthms size 7?

Close. UK N to O sits around 17.3 mm, which is our size 7. Letter sizes are half a size apart, so some letters fall between our numbers. When that happens, go down.

Can I use a printable ring sizer?

You can, but printers scale pages. Check the printed ruler against a real one before you trust it. The paper-strip method is more reliable.

My knuckle is much bigger than the base of my finger.

Measure both, pick the size between them, closer to the base. Silicone is forgiving over a knuckle in a way metal is not.

Does the ring stretch permanently?

A little, over the first week, which is why we say go down. After that it holds its size until it is worn out.