How to measure your ring size at home
Two methods, both about two minutes. One needs a ring that already fits; the other needs a strip of paper. Both need a bank card, because that is what makes the screen below measure in real millimetres instead of pixels.
Measuring is the easy part. The part that goes wrong is measuring the inside of the ring rather than the outside, and measuring the finger at the wrong time of day. Both are covered below.
Measure it now
Calibrate once with any bank card, then use whichever method you have to hand. Nothing is uploaded and nothing is stored except your screen’s scale, which stays in your browser.
Interactive ring sizer
Calibrate Screen Scale
Hold any standard bank card upright against your screen and adjust the slider until the outline matches its exact width (53.98 mm).
Hold a bank card against the screen and line its short edge up between the two bars
53.98 mm
1:1 Physical Scale Outline
Inside Diameter
Your Size Is
Why UK and India can differ from your jeweller’s chart
Published UK letter charts vary by up to half a size, because British scales do not all include the same half letters. Ours follows BS EN 28653 exactly. If your jeweller uses a different chart, give them the circumference in millimetres above instead.
India has no official ring size standard. Four Indian jewellers we checked number rings by inner circumference in millimetres minus 40, and that is what we show. Tanishq publishes a chart that runs about one size smaller. Give your jeweller the diameter in millimetres - that number is unambiguous.
Method 1 — a ring that already fits
This is the more accurate method, because a ring is a rigid object and a finger is not. Use a ring worn on the same finger of the same hand — hands differ, and so do fingers.
- 1. Calibrate the screen. Hold any bank card upright against the screen and drag the slider until the outline matches its edges. Every card is 85.60 × 53.98 mm by ISO/IEC 7810, which is what turns pixels into millimetres. Keep browser zoom at 100%.
- 2. Lay the ring on the circle. Adjust the circle until its outer edge touches the inside edge of your ring.
- 3. Read every size at once. The result is inner diameter, and every national size computed from it.
The commonest mistake: measuring the outside of the band. You are measuring the space your finger occupies, not the metal around it. On a wide, thick band the difference is easily a full size.
Method 2 — a strip of paper
Use this when there is no ring to copy. You are measuring the circumference— the distance around the finger — and the tool converts it for you.
- 1. Cut a strip about 1 cm wide. Narrower strips twist and read short; wider ones will not sit flat.
- 2. Wrap it round the base of the finger. Snug and flat against the skin, with no slack and no pull. Mark where it overlaps.
- 3. Check it passes the knuckle. Before unwrapping, slide the loop off over the knuckle. If it will not go, the ring will not either — widen it until it just passes, and use that.
- 4. Flatten and measure to the mark, then set the tool above to Circumference and type the length in.
Why string gives the wrong answer
String, thread, dental floss and ribbon are all suggested constantly, and all share one problem: they stretch. Pulled taut round a finger, a length of string reads shorter than the finger actually is, and the error runs one way — always too small.
The arithmetic is unforgiving. One full US size is 0.81 mm of diameter, which is only 2.55 mm of circumference — about two and a half millimetres. Stretch a string by that much, which takes almost no force, and you have lost a whole size.
Paper does not stretch. If string is genuinely all you have, use it to mark the length and then measure the string flat against a ruler without tension — and treat the answer as approximate.
Measuring in centimetres or inches
Use whatever your ruler is marked in — the tool takes all three, and they are the same measurement written differently. Set the unit switcher above and type your number in.
One warning about inches. A quarter US size is 0.2032 mm of diameter, which is about 0.008 inches. An inch ruler marked in sixteenths cannot resolve that, and neither can a figure written to two decimal places. If you have a choice, measure in millimetres.
What your strip length means
Common paper-strip lengths and the sizes they come to. Every row is computed from the published standards, not copied from a chart. For anything between these, use the tool.
| Strip length | In mm | In inches | Diameter | US | UK | EU / ISO |
|---|---|---|---|---|---|---|
| 4.5 cm | 45 mm | 1.77 in | 14.32 mm | 3¼ | G | 45 |
| 5.0 cm | 50 mm | 1.97 in | 15.92 mm | 5¼ | K | 50 |
| 5.5 cm | 55 mm | 2.17 in | 17.51 mm | 7¼ | O | 55 |
| 6.0 cm | 60 mm | 2.36 in | 19.10 mm | 9¼ | S | 60 |
| 6.5 cm | 65 mm | 2.56 in | 20.69 mm | 11¼ | W | 65 |
| 7.0 cm | 70 mm | 2.76 in | 22.28 mm | 13 | Z+1 | 70 |
An em dash means that scale does not define a size there — it is not a gap in our data. Every system has a bottom and a top, and we would rather print nothing than invent a number.
If you cannot measure at all
Usually this means buying for someone else without asking. Ranked by how well they work:
- Borrow a ring they already wear. Measure it with method 1 and put it back. This is the only approach that is actually accurate. Note which finger it came from.
- Press one into soap or clay and measure the inner edge of the impression. Works, loses a little precision.
- Ask someone who would know — a sibling, a close friend. Less romantic, far more reliable than any guess.
- Fall back on the average.US 6 (16.51 mm) and US 9 (18.95 mm) are the commonly cited averages for women and men. This is a guess dressed as a number, and it is the reason engagement rings get resized so often — but if you must guess, guess here, and buy from somewhere that resizes.
Tracing round the outside of a finger with a pen does not work, and neither does comparing hand size. Both are widely repeated and neither survives contact with a ruler.
When to measure, and how tight is right
Fingers are not a fixed size. They swell in heat, after exercise, after salt, and late in the day; they shrink in cold. The swing across a single day is easily half a size, which is more than the difference the tool is resolving.
- Measure at the end of the day, at normal room temperature.
- Measure the same finger on the same hand you will wear the ring on.
- Measure two or three times on different days and take the largest.
A ring fits when it goes on with slight resistance, sits without pinching, and needs a small deliberate tug to come off. If it slides off freely it is too big — losing a ring is worse than a snug one. If your knuckle is much wider than the base of your finger, size to the knuckle: the ring has to get past it.
No screen to hand?
Print a paper ring sizerinstead — it carries a scale-check square so you can prove your printer did not shrink the page, which most printable sizers quietly skip.
Measuring ring size: common questions
Taken word for word from Google’s “People also ask”. Nothing here is invented to pad the page.
What is the easiest way to measure ring size at home?
Copy a ring that already fits. It is rigid, it does not swell, and it takes under a minute: calibrate the screen against a bank card, then match the on-screen circle to the ring's inside edge. Measuring a finger is the fallback, not the first choice.
How can I measure my ring size at home without a ruler?
Use the calibrated circle on this page — a bank card replaces the ruler, because every card is 85.60 × 53.98 mm by ISO/IEC 7810. Lay a ring on the circle and adjust until they match. If you have no ring either, wrap a strip of paper round the finger, mark the overlap, then measure the strip against the same calibrated scale.
How to check ring size with thread?
You can, but expect it to read small. Thread and string stretch under the tension of wrapping, and one full US size is only 2.55 mm of circumference — a stretch you would not feel. Paper does not stretch. If thread is all you have, mark it, lay it flat with no tension and measure it then.
What size ring do I wear if my finger is 2.5 inches?
2.5 inches around is 63.5 mm of circumference, or 20.21 mm of diameter — about US 10½, UK V, EU 64. Note that 2.5 inches is a circumference, not a diameter; mixing the two up puts you out by roughly three times.
What is my ring size if the string is 2.5 inches?
Nominally US 10½ — 63.5 mm of circumference. But if that 2.5 inches came off string rather than paper, treat it as a floor rather than an answer: string stretches as you pull it round, and the error always runs the same way, making the finger read smaller than it is.
How big is a 7 size ring?
17.32 mm across the inside and 54.42 mm around — roughly the diameter of a AA battery. It is one size above the most commonly sold women's size and two below the most common men's, so it sits in the middle of what jewellers stock rather than at either end.
How can I find out my husband's ring size without him knowing?
Borrow a ring he already wears and measure it here — it is the only method that is genuinely accurate, and it takes two minutes. Failing that, press one into a bar of soap and measure the impression, or ask someone close to him. Tracing round his finger with a pen and comparing hand sizes both sound reasonable and neither survives contact with a ruler.