UK Ring Size Guide & Chart

Every ring we make is crafted to your size at no extra cost, in every UK size from F to Z, half sizes included. The chart below converts UK letters to US and EU sizes and to millimetres, and the three methods underneath let you check your size at home. You do not need to go anywhere to be measured.

Let us send you a strap sizer

An adjustable strap sizer marked in UK letters, sent by next-day delivery. It is £5 at checkout, and we email the full £5 straight back to you as credit towards your ring.

Order a strap sizer — £5 Sent within one working day · credit never expires · works alongside any other offer

UK ring size chart

UK ring sizes run in letters. Under the British Standard for ring sizes (BS 6820), each full letter adds 1.25mm to the inside circumference of a ring and each half size adds 0.625mm. EU sizes are simply the inside circumference in millimetres, rounded to the nearest whole number, and the US column shows the nearest quarter size.

UK US EU Inside circumference Inside diameter
F 2¾ 44 43.75 mm 13.9 mm
F½ 3 44 44.38 mm 14.1 mm
G 3¼ 45 45.00 mm 14.3 mm
G½ 3½ 46 45.63 mm 14.5 mm
H 3¾ 46 46.25 mm 14.7 mm
H½ 4 47 46.88 mm 14.9 mm
I 4¼ 48 47.50 mm 15.1 mm
I½ 4½ 48 48.13 mm 15.3 mm
J 4¾ 49 48.75 mm 15.5 mm
J½ 5 49 49.38 mm 15.7 mm
K 5¼ 50 50.00 mm 15.9 mm
K½ 5½ 51 50.63 mm 16.1 mm
L 5¾ 51 51.25 mm 16.3 mm
L½ 6 52 51.88 mm 16.5 mm
M 6¼ 53 52.50 mm 16.7 mm
M½ 6½ 53 53.13 mm 16.9 mm
N 6¾ 54 53.75 mm 17.1 mm
N½ 7 54 54.38 mm 17.3 mm
O 7¼ 55 55.00 mm 17.5 mm
O½ 7½ 56 55.63 mm 17.7 mm
P 7¾ 56 56.25 mm 17.9 mm
P½ 8 57 56.88 mm 18.1 mm
Q 8¼ 58 57.50 mm 18.3 mm
Q½ 8½ 58 58.13 mm 18.5 mm
R 8¾ 59 58.75 mm 18.7 mm
R½ 9 59 59.38 mm 18.9 mm
S 9¼ 60 60.00 mm 19.1 mm
S½ 9½ 61 60.63 mm 19.3 mm
T 9¾ 61 61.25 mm 19.5 mm
T½ 10 62 61.88 mm 19.7 mm
U 10¼ 63 62.50 mm 19.9 mm
U½ 10½ 63 63.13 mm 20.1 mm
V 10¾ 64 63.75 mm 20.3 mm
V½ 11 64 64.38 mm 20.5 mm
W 11¼ 65 65.00 mm 20.7 mm
W½ 11½ 66 65.63 mm 20.9 mm
X 11¾ 66 66.25 mm 21.1 mm
X½ 12 67 66.88 mm 21.3 mm
Y 12 68 67.50 mm 21.5 mm
Y½ 12¼ 68 68.13 mm 21.7 mm
Z 12½ 69 68.75 mm 21.9 mm

Need a size smaller than F or larger than Z? Email us before you order and we will tell you what is possible.

Quick conversions

US to UK ring sizes

  • US 4 is a UK H½, and US 5 is a UK J½.
  • US 6 is a UK L½, and US 7 is a UK N½.
  • US 8 is a UK P½, and US 9 is a UK R½.
  • US 10 is a UK T½, and US 11 is a UK V½.
  • US half sizes land on the UK half size in between: US 6½ is a UK M½ and US 7½ is a UK O½.

EU to UK ring sizes

  • EU 48 is a UK I½, and EU 50 is a UK K.
  • EU 52 is a UK L½, and EU 54 is a UK N.
  • EU 56 is a UK P, and EU 58 is a UK Q½.
  • EU 60 is a UK S, and EU 62 is a UK T½.

UK letters in millimetres

  • Size J is 48.75mm around the inside and 15.5mm across.
  • Size L is 51.25mm around and 16.3mm across, and size M is 52.5mm around and 16.7mm across.
  • Size N is 53.75mm around and 17.1mm across, and size P is 56.25mm around and 17.9mm across.

Three ways to find your size at home

1. Measure a ring that already fits

The most reliable method that costs nothing, and it does not spoil a surprise.

  1. Take a ring that fits the correct finger comfortably, on the same hand.
  2. Lay it flat and measure straight across the inside of the band, edge to edge, in millimetres.
  3. Find that measurement in the Inside diameter column of the chart.

A ruler works, but a digital caliper is far more accurate if you can borrow one. One millimetre across is about two and a half sizes, so measure twice.

2. Use a strap sizer

A strap sizer is an adjustable band marked in UK letter sizes. You slide it onto the finger, ease it closed until it sits the way a ring should, and read your size from the window. It goes on and off over the real knuckle, which a paper strip cannot do. Order one from us: we send it within one working day by next-day delivery, it is £5 at checkout, and the full £5 comes back to you as credit the moment your order is paid. The credit does not expire and stacks with any other offer, including your first-order discount.

  • Do not pull it tight. Close it until it is snug and no further. Over-tightening is the commonest reason people end up half a size too small.
  • Check it comes back off over the knuckle. A ring has to pass the knuckle every time it is worn.
  • Measure late in the day, with warm hands.

3. Measure the finger with a strip of paper

  1. Cut a thin strip of paper about 5mm wide.
  2. Wrap it around the base of the finger, snug but loose enough to slide over the knuckle.
  3. Mark where the paper overlaps, unwrap it, and measure to the mark in millimetres.
  4. That number is the Inside circumference. Find it in the chart.

Paper can stretch and tension is hard to judge, so repeat it three times and use the average.

Four things that change the answer

  • Time of day. Fingers are smallest first thing in the morning and largest in the evening. Measure late in the day.
  • Temperature. Cold fingers shrink. Never measure with cold hands.
  • Knuckles. If the knuckle is much wider than the base of the finger, size for the knuckle, because the ring has to get over it.
  • Wide bands. A band over about 6mm wide feels tighter. Go up half a size.

If you fall between two sizes, choose the larger one. A ring that is slightly loose can be worn; one that will not pass the knuckle cannot.

Your questions

Are UK and US ring sizes the same? No. UK sizes are letters and US sizes are numbers, and the two scales step at slightly different rates, so the US column shows the nearest match. If you only know a US size and want to be certain, email us the number and we will confirm the UK letter before we make anything.

How much bigger is a half size? A half size adds 0.625mm to the inside circumference, about 0.2mm across the inside of the ring. Half sizes are available on every ring we make.

How do I find a ring size for a surprise proposal? Borrow a ring they already wear and measure it, or ask a trusted friend to help. Our guide to finding a ring size at home has three quiet tactics.

Still not sure?

Do not guess on an engagement ring. You have two options:

  • Order a strap sizer and measure properly at home. The £5 comes straight back to you as credit.
  • Email info@thelabjewellers.com with what you know, whether that is a diameter, a US size or the ring you measured, and we will work it out with you. We reply personally, within two working days.

Because every piece is made to order in your chosen size, getting this right before you order saves the most time. Nothing goes into production until your size is confirmed in writing. If a ring does arrive and the fit is wrong, contact us and we will talk you through the options.