Ring sizer
Check this first. Hold a bank card against the box below. If it does not match, your printer scaled the page: print again at 100% scale with "fit to page" switched off. Nothing else on this sheet is usable until the card matches.
Method 1 — the strip
Cut along the line, wrap it snugly around the base of your finger, and read the size at the overlap. Measure at the end of the day, in a warm room.
Method 2 — the circles
Lay a ring that already fits over these circles. The right one is the circle whose line just disappears inside the ring.
Ring sizer from Sagely Chic. Sizes shown are US, then UK.
Ring sizing looks like it should be the simplest conversion in fashion. One number, one finger. In practice it is the one where published charts disagree with each other most, and where the number that finally matters — whether the ring goes over your knuckle — is not on any chart at all.
This calculator works from the inside circumference of your finger in millimetres rather than by adding a fixed number to a size label. Here is why that matters, and what to do about a knuckle that has thickened.
Why ring size charts disagree with each other
Because the four systems in common use do not count in the same unit. They do not even count the same thing — two measure across the ring and two measure around it.
Size 0 is an inside diameter of 0.458 in, and every whole size adds 0.032 in. That is 0.81 mm across, or 2.55 mm around.
Size A is an inside circumference of 37.5 mm, and each letter adds 1.25 mm. Half letters add 0.625 mm.
Under ISO 8653 the size is the inside circumference in millimetres. A size 54 ring measures 54 mm around. Nothing to convert.
JIS size 1 is 13.0 mm across and each size adds one third of a millimetre of diameter — about 1.05 mm around.
Now put two of those side by side. One US size is 2.5535 mm of circumference. One British letter is 1.25 mm. Divide one by the other and you get 2.0428 letters per US size — not two.
Ten US sizes should span twenty letters. They actually span 20.43. That extra four tenths of a letter is why a chart built on “two letters per size” is right in the middle and half a letter out at the ends — and why the letter on your jeweller’s steel sizer sometimes disagrees with the letter on the website.
There is a second, less forgivable reason charts disagree. Some widely copied “UK” tables are not British scales at all — they are US charts with letters pasted on top. You can spot one in a few seconds: work out the millimetres between consecutive letters. A real British scale gives 1.25 mm every time. The copied ones wander between about 1.12 and 1.28, because the numbers underneath are really US sizes.
Ring size chart
Inside circumference is the column that matters. Everything to its left is a label somebody chose; the circumference is the ring.
| US | UK / AU | EU (ISO) | France | Japan | Inside diameter | Inside circumference |
|---|---|---|---|---|---|---|
| 3 | F½ | 44 | 4 | 4 | 14.1 mm | 44.2 mm |
| 3.5 | G½ | 45 | 5 | 5 | 14.5 mm | 45.5 mm |
| 4 | H½ | 47 | 7 | 7 | 14.9 mm | 46.8 mm |
| 4.5 | I½ | 48 | 8 | 8 | 15.3 mm | 48.0 mm |
| 5 | J½ | 49 | 9 | 9 | 15.7 mm | 49.3 mm |
| 5.5 | K½ | 51 | 11 | 10 | 16.1 mm | 50.6 mm |
| 6 | L½ | 52 | 12 | 12 | 16.5 mm | 51.9 mm |
| 6.5 | M½ | 53 | 13 | 13 | 16.9 mm | 53.1 mm |
| 7 | N½ | 54 | 14 | 14 | 17.3 mm | 54.4 mm |
| 7.5 | O½ | 56 | 16 | 15 | 17.7 mm | 55.7 mm |
| 8 | P½ | 57 | 17 | 16 | 18.1 mm | 57.0 mm |
| 8.5 | Q½ | 58 | 18 | 18 | 18.5 mm | 58.3 mm |
| 9 | R½ | 60 | 20 | 19 | 18.9 mm | 59.5 mm |
| 9.5 | S½ | 61 | 21 | 20 | 19.4 mm | 60.8 mm |
| 10 | T½ | 62 | 22 | 21 | 19.8 mm | 62.1 mm |
| 10.5 | U½ | 63 | 23 | 23 | 20.2 mm | 63.4 mm |
| 11 | V½ | 65 | 25 | 24 | 20.6 mm | 64.6 mm |
| 11.5 | W½ | 66 | 26 | 25 | 21.0 mm | 65.9 mm |
| 12 | Y | 67 | 27 | 26 | 21.4 mm | 67.2 mm |
| 12.5 | Z | 68 | 28 | 27 | 21.8 mm | 68.5 mm |
| 13 | Z+1 | 70 | 30 | 29 | 22.2 mm | 69.7 mm |
One thing that is not in this table, because it does not exist: a men’s and women’s scale. Unlike shoes or clothes, rings have no gendered sizing anywhere in the world. A size 7 is a size 7. Men’s rings simply cluster higher up the same scale, and are more often cut in wider bands.
The knuckle problem
Here is the thing no chart can tell you. A ring has to do two contradictory jobs: pass over your knuckle and then sit still at the base of your finger. For most people under about forty those two measurements are close enough that one size does both. After that, they very often are not.
Knuckles thicken with age, and they usually thicken faster than the finger beneath them. Osteoarthritis in the finger joints accelerates it. The result is the complaint we hear constantly: the ring still fits my finger, it just will not go on any more. That is not a sizing mistake. It is a fitting problem, and it has proper solutions.
Measure both places — the base of the finger and the widest part of the knuckle — and enter both in the calculator above. What you do next depends on the gap between them.
Size to the base of the finger and buy normally. Your knuckle is not the constraint.
Take a size between the two, nearer the knuckle. It will turn a little in cold weather and settle as the day warms up. Most people live with this happily.
Size to clear the knuckle, then have two small beads soldered inside the shank. They hold the ring upright at the base without stopping it going on. Quick, inexpensive and completely reversible.
More than two and a half sizes of gap. Beads will not be enough. Ask for a hinged or spring-loaded shank, which opens to clear the knuckle and closes at the base. Do not buy a plain band online in this situation.
All four of those are ordinary jewellery-bench work. If a shop tells you nothing can be done, try a different shop — ideally one with a workshop on the premises rather than one that sends everything away.
How to measure your ring size at home
There are three reliable ways and one popular way that is not reliable at all.
Method 1: a strip of paper
Cut a strip of paper about 5 mm wide. Wrap it snugly around the base of the finger, mark where it overlaps, lay it flat and measure to the mark in millimetres. That length is your inside circumference — enter it directly.
Not string, and not dental floss. String stretches under tension and floss cuts into the skin, so both read small — and a ring ordered small is the one failure this whole page exists to prevent. Paper does neither.
Method 2: a ring you already own
Measure straight across the inside of the opening in millimetres — the inside diameter, not the outside of the band. The calculator above also has an on-screen sizer for this: you match a bank card to set the scale of your display, then lay the ring against a circle. Every bank card in the world is the same size to a fraction of a millimetre, which makes it a better ruler than most rulers.
Be honest about which finger the ring actually fits. A ring from your right middle finger tells you very little about your left ring finger.
Method 3: print the sizer
The calculator will print a sheet with a wrap-around strip and a set of true-size circles. Print it at 100% scale with “fit to page” switched off, then hold a bank card against the box on the sheet. If the card does not match the box, the printer scaled the page and nothing on that sheet is usable — print it again.
Whichever method you use
- Measure at the end of the day. Fingers are smallest first thing in the morning. The difference across one day is easily half a size.
- Measure warm. Cold hands can read a full size small. If you have just come in from outside, wait.
- Measure three times, on different days, and take the largest reading.
- Round up, never down. A ring slightly too large can be beaded, padded or resized down for very little. One slightly too small may never pass the knuckle, and no amount of money fixes that on the day.
Wide bands fit tighter
The same nominal size feels noticeably tighter in a wide band, because more of the metal is gripping more of the finger and there is less room for the soft tissue to move. This catches people out when they swap a thin band for a statement one.
- Under 3 mm — no adjustment. Your measured size is the size to order.
- 3 to 5 mm — about a quarter size up. Many jewellers will cut a quarter size on request even when the shop chart only lists halves.
- 6 to 8 mm — half a size up, and ask for a comfort fit: a domed inner edge that gives back roughly the room a wide band takes away.
- Over 8 mm — half to three quarters of a size up, and treat comfort fit as essential rather than optional.
The calculator applies this for you if you tell it the band width, so the size it shows is the size to order rather than a number you then have to adjust yourself.
What changes after 50
Quite a lot, and none of it is a sign that anything is wrong.
- Knuckles thicken. Often faster than the finger, which is the whole knuckle problem above.
- Fingers swell and shrink much more than they used to. Heat, salt, a long flight, blood pressure medication, thyroid changes and ordinary fluid retention each move a finger by up to a full size in a day.
- A long-worn ring can be wrong in both directions at once — loose at the base and tight at the knuckle. Beads solve exactly this, and it is a bench job, not a reason to stop wearing it.
- A slightly wider comfort-fit band is kinder to an aching joint, because it spreads the pressure. Just size for the width.
- If a ring is genuinely stuck, do not force it. Cold water, the arm raised for a minute, then soap or hand cream twists it off in most cases. A jeweller can cut and repair a ring far more cheaply than an emergency department can.
Which rings cannot be resized
Worth knowing before you buy, because it changes how much the size has to be right first time.
| Ring | Can it be resized? |
|---|---|
| Plain gold, silver or platinum band | Yes — routinely, usually a size or two either way |
| Solitaire with a plain shank | Yes — the shank is untouched by the setting |
| Channel-set stones, inlays, engraving all round | Sometimes — a size or so, at a price worth asking about first |
| Eternity ring, stones the whole way round | No — there is no plain section to cut. Remaking is the only route |
| Tension setting | No — the metal’s spring holds the stone; cutting it changes that |
| Titanium, tungsten carbide, ceramic | No — tungsten and ceramic shatter rather than stretch |
One more thing about resizing up: stretching thins the metal. If a ring needs more than about two sizes, ask for material to be added to the shank rather than the shank stretched. It costs more and lasts far longer.
European brands and the number stamped inside
If you have ever looked at a Cartier or Bulgari ring listed as a 54 and wondered what scale that is, the answer is delightfully simple: it is not a model number and it is not a size code. It is the inside circumference in millimetres, under ISO 8653. A 54 measures 54 mm around the inside, which is a US 7.
That makes European sizing the most useful of the four systems when you are buying internationally, for exactly the same reason that centimetres beat shoe sizes: the number is a measurement rather than a label, so it cannot mean two different things in two different countries.
Common questions
What is the average ring size for a woman?
US 6 to 7 is the range usually quoted, with 6 the single most common. It is a genuinely useless number for buying a specific ring for a specific person, though. Half of everyone is outside it, and the gap between a 6 and a 7 is the gap between a ring that fits and one that does not. Borrow a ring she already wears and measure the inside diameter instead.
Are men’s and women’s ring sizes different?
No. Unlike shoes and clothing, ring sizing has no gendered scale in any country. The same number means the same measurement whoever is wearing it. Men’s ring sizes simply tend to fall higher up the scale, typically US 8 to 12 against US 5 to 8, and men’s rings are more often cut in wider bands — which does affect the fit, as above.
Why does your chart say a different UK letter to the one I found elsewhere?
Because we calculate the letter from the British Standard — size A at 37.5 mm of circumference, 1.25 mm per letter — rather than assuming two letters per US size. At the middle of the range the two approaches agree. Towards the ends they drift apart by about half a letter, and popular charts disagree with each other by a full letter at some sizes. Our answer is the one that matches a jeweller’s physical sizing rings, because those are made to the same standard.
Should I size up or down if I am between sizes?
Up, always. This is the opposite of a close call. A ring that runs slightly large can be beaded, padded, or resized down cheaply. A ring that runs slightly small may simply not go over the knuckle, and on the day that matters there is nothing to be done about it. The calculator tells you when your measurement falls between two sizes.
How can I find someone’s ring size without asking?
Borrow a ring she wears on the intended finger and measure the inside diameter with a ruler, or lay it on the on-screen sizer above. Failing that, press it into a bar of soap and measure the impression. Do not guess from a photograph, and be careful about “she is about my size” — finger size correlates poorly with height, build or dress size.
Can I measure my ring size on screen accurately?
Yes, provided you calibrate it first, which is what the bank card step does. There is no fixed relationship between a screen pixel and a millimetre — browser zoom, device pixel ratio and display scaling all change it, and none of them announce themselves. Matching a card sets the scale for your screen as it is right now. Re-check it if you zoom the page, rotate a tablet, or come back on a different device. Any tool that shows you a “true size” circle without calibrating first is guessing.
Are my measurements saved?
No. What you enter is sent to our server to be converted and used only to produce the result on screen. Nothing is stored, logged against you or shared. The one thing your browser does remember is your screen calibration, which stays on your own device and never reaches us.
