The 4Cs — What You'll Actually See
Know what you're looking at before a jeweller explains it to you on their terms
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Ring size chart
UK ring size chart
Every UK ring size from A to Z in millimetres, with US and EU equivalents. Plus how to measure your own finger at home, and how to find someone else's size without asking.
PK
Parth KananiSeptember 2026 · 5 min read
In short: UK ring sizes run from A to Z in half sizes. Each letter adds about 1.23mm around the finger. Most women in the UK wear L to N and most men wear R to T. A UK M is US 6¼ and EU 53.
The chart
Every UK ring size, A to Z
Diameter is across the inside of the ring. Circumference is the distance around your finger. EU sizes are the circumference in millimetres. Charts from different jewellers can differ by a few tenths of a millimetre.
| UK | US | EU | Diameter | Circumference |
|---|---|---|---|---|
| A | ½ | 38 | 12mm | 37.8mm |
| A½ | ¾ | 38 | 12.2mm | 38.4mm |
| B | 1 | 39 | 12.4mm | 39mm |
| B½ | 1¼ | 40 | 12.6mm | 39.6mm |
| C | 1½ | 40 | 12.8mm | 40.3mm |
| C½ | 1¾ | 41 | 13mm | 40.9mm |
| D | 2 | 41 | 13.2mm | 41.5mm |
| D½ | 2¼ | 42 | 13.4mm | 42.1mm |
| E | 2½ | 43 | 13.6mm | 42.7mm |
| E½ | 2¾ | 43 | 13.8mm | 43.3mm |
| F | 3 | 44 | 14mm | 43.9mm |
| F½ | 3¼ | 45 | 14.2mm | 44.6mm |
| G | 3½ | 45 | 14.4mm | 45.2mm |
| G½ | 3½ | 46 | 14.6mm | 45.8mm |
| H | 3¾ | 46 | 14.8mm | 46.4mm |
| H½ | 4 | 47 | 15mm | 47mm |
| I | 4¼ | 48 | 15.2mm | 47.6mm |
| I½ | 4½ | 48 | 15.4mm | 48.2mm |
| J | 4¾ | 49 | 15.6mm | 48.9mm |
| J½ | 5 | 49 | 15.7mm | 49.5mm |
| K | 5¼ | 50 | 15.9mm | 50.1mm |
| K½ | 5½ | 51 | 16.1mm | 50.7mm |
| Lcommon (women) | 5¾ | 51 | 16.3mm | 51.3mm |
| L½ | 6 | 52 | 16.5mm | 51.9mm |
| Mcommon (women) | 6¼ | 53 | 16.7mm | 52.5mm |
| M½ | 6½ | 53 | 16.9mm | 53.2mm |
| Ncommon (women) | 6¾ | 54 | 17.1mm | 53.8mm |
| N½ | 7 | 54 | 17.3mm | 54.4mm |
| O | 7¼ | 55 | 17.5mm | 55mm |
| O½ | 7½ | 56 | 17.7mm | 55.6mm |
| P | 7¾ | 56 | 17.9mm | 56.2mm |
| P½ | 8 | 57 | 18.1mm | 56.8mm |
| Q | 8¼ | 57 | 18.3mm | 57.4mm |
| Q½ | 8½ | 58 | 18.5mm | 58.1mm |
| Rcommon (men) | 8¾ | 59 | 18.7mm | 58.7mm |
| R½ | 9 | 59 | 18.9mm | 59.3mm |
| Scommon (men) | 9¼ | 60 | 19.1mm | 59.9mm |
| S½ | 9½ | 61 | 19.3mm | 60.5mm |
| Tcommon (men) | 9¾ | 61 | 19.5mm | 61.1mm |
| T½ | 10 | 62 | 19.7mm | 61.7mm |
| U | 10 | 62 | 19.8mm | 62.4mm |
| U½ | 10¼ | 63 | 20mm | 63mm |
| V | 10½ | 64 | 20.2mm | 63.6mm |
| V½ | 10¾ | 64 | 20.4mm | 64.2mm |
| W | 11 | 65 | 20.6mm | 64.8mm |
| W½ | 11¼ | 65 | 20.8mm | 65.4mm |
| X | 11½ | 66 | 21mm | 66mm |
| X½ | 11¾ | 67 | 21.2mm | 66.7mm |
| Y | 12 | 67 | 21.4mm | 67.3mm |
| Y½ | 12¼ | 68 | 21.6mm | 67.9mm |
| Z | 12½ | 69 | 21.8mm | 68.5mm |
Common sizes as reported by UK jewellers, Oct 2026. Sizes above Z are written Z+1, Z+2 and so on.
How to measure
Three ways to find your ring size at home
Match a ring on screen
Calibrate your screen with a bank card, then match a ring that fits. Takes two minutes.
Open the ring sizerPaper or string
Wrap a thin strip around the base of your finger, mark where it meets, and measure it in mm. That length is your circumference: find it in the chart above.
Print a ring sizer
A free A4 sizer with a strip and circles, printed at actual size, with a bank-card check.
Print the ring sizerMeasure at the end of the day, when fingers are slightly larger, and not when you're cold. The ring has to slide over your knuckle, so if your knuckles are much wider than the base of your finger, size up. Between two sizes? Choose the larger one.
Conversion
US to UK ring size
Buying from a US brand? Each US size is roughly two UK letters.
US 3
UK F
US 3.5
UK G
US 4
UK H½
US 4.5
UK I½
US 5
UK J½
US 5.5
UK K½
US 6
UK L½
US 6.5
UK M½
US 7
UK N½
US 7.5
UK O½
US 8
UK P½
US 8.5
UK Q½
US 9
UK R½
US 9.5
UK S½
US 10
UK U
US 10.5
UK V
US 11
UK W
US 11.5
UK X
US 12
UK Y
US 12.5
UK Z
US 13
UK Z
Planning a surprise?
How to find someone else's ring size without asking
The proposal should be a surprise. The ring size shouldn't be a gamble. Four ways to find out without giving the game away.
Method 1
Borrow a ring she already wears
This is the most reliable method — and the one most people overcomplicate. Here's exactly how to do it.
The most reliable method
- Pick a ring she wears on her right ring finger. The right ring finger is usually very close in size to the left ring finger — close enough for a jeweller to work with. Don't use a ring from her index finger or thumb — those are typically 1-2 sizes larger.
- Borrow it for a day. Take it when she's in the shower or asleep. Press it into a bar of soap to capture the inner diameter, or simply trace the inside circle on a piece of paper with a thin pen. Return the ring before she notices.
- Take it to a jeweller. If you can take the actual ring to a Hatton Garden jeweller, they'll measure it on a mandrel in seconds. This gives you an exact size — no guesswork, no conversion charts.
Method 2
The string and paper trick
If you can't borrow a ring, you can measure the inner circumference of one she owns — or, if you're measuring her finger directly (less secretive, but effective if she's asleep), here's how.
1
Cut a thin strip of paper or use a piece of string
About 10cm long and no wider than 5mm. A strip cut from a Post-it note works perfectly.
2
Wrap it around the inside of her ring
Thread the paper or string through the ring and wrap it snugly against the inner wall. Mark where the strip overlaps with a pen.
3
Measure the length in millimetres
Lay the strip flat and measure from the end to the pen mark with a ruler. This gives you the circumference. Divide by 3.14 (pi) to get the diameter. Match the diameter to the chart below.
4
If you're between sizes, go up
A slightly loose ring is always better than a slightly tight one. It's easier and less noticeable to resize down.
Method 3
Ask her best friend
Her best friend either knows her ring size, can find out without raising suspicion, or will be thrilled to be part of the mission. The trick is asking the right way.
Pre-written WhatsApp message
Copy this and send it. We've written it so it sounds natural and gives her friend a clear mission:
"Hey — I need your help with something and you absolutely cannot tell [her name]. I'm getting an engagement ring and I need to find out her ring size without her knowing. Can you find out? Maybe suggest trying on each other's rings, or go jewellery shopping together and get her to try something on? Even a rough size would help — the jeweller can resize within a size or two. Let me know if you're in."
Important: Only ask someone you genuinely trust to keep this secret. And give them a deadline — "I need to know by next Friday" — or it'll drift.
Method 4
Use our ring size tool
If you have one of her rings to hand, our on-screen ring size tool lets you measure it digitally — place the ring on screen, match the circle, and get an instant UK size reading.
Try the Ring Size Finder
Place her ring on screen and match the circle. Takes 30 seconds.
Open toolDon't panic
If you get it wrong — it's fine
Here's the reality that nobody tells you: getting the ring size slightly wrong is completely normal, and every jeweller is prepared for it.
What actually happens
- Within 1-2 sizes: Most Hatton Garden jewellers will resize for free. It takes 1-3 days and is completely invisible — no marks, no weakness, no visible change. This is the most common scenario.
- Beyond 2 sizes: Still possible, but it may cost £50-£100 and requires more work. Some intricate settings (like full pave bands) are harder to resize. The jeweller will tell you upfront if there are limitations.
- The proposal still works. Even if the ring doesn't fit perfectly on the night, it goes on the finger for the moment — and you go back together the next week to have it adjusted. Many couples actually enjoy the sizing appointment. It's part of the story.
Our advice: Don't let ring size anxiety delay the proposal. Get as close as you can using the methods above, round up if you're unsure, and trust that resizing is routine. Every jeweller in Hatton Garden does it daily.
Related guides
Keep going — there's more to figure out before you buy.
Common Questions
What is the average ring size in the UK?+
UK jewellers report most women’s ring sizes fall between L and N, with M the most common. Men’s usually fall between R and T, with S the most common. Averages are only a starting point; measure if you can.
How do I convert a US ring size to UK?+
Find the US size in the chart and read across. US 6 is a UK L½, US 7 is a UK N½ and US 8 is a UK P½. US sizes go up in steps of 2.55mm around the finger; UK letters go up in steps of about 1.23mm, so each US size is roughly two UK letters.
Can an engagement ring be resized after purchase?+
Yes — most rings can be resized up or down by 1-2 sizes without any visible change to the ring. Most Hatton Garden jewellers offer the first resize free within the first few months. Going beyond 2 sizes can affect the ring's structural integrity or require more significant rework, which is why getting close matters.
Does finger size change throughout the day?+
Yes. Fingers swell slightly in warm weather, after exercise, and in the evening. They shrink in cold weather and first thing in the morning. The difference can be half a size either way. If you're measuring, aim for mid-afternoon on a normal-temperature day for the most accurate reading.
Should I size up or down if I'm between sizes?+
Size up. A slightly loose ring is comfortable and easy to resize down. A too-tight ring is uncomfortable from the moment it goes on, and she'll know immediately that you guessed wrong. It's always easier (and less noticeable) to make a ring smaller than to stretch it larger.