Ring size calculator: measure at home
Type a measurement and the sizes appear here.
Sizes are for guidance, following BS 6820 and ISO 8653 as checked on 2026-10-23. Brands cut sizes differently: try the ring on or ask your jeweller before you buy. Disclaimer
Wrap something round your finger, measure the length, type it in. No printer and no ring needed.
How to measure ring size with string or paper
Example: a strip marked at 54.4 mm is US 7, UK N½, EU/ISO 54 and 14号.
- Cut a strip of paper about 5 mm wide and 100 mm long, or take a length of string or dental floss. Paper is easier to read than string, which stretches.
- Wrap it round the base of the finger. Snug, not tight: you should feel it, but it must still slide over the knuckle.
- Mark where the end overlaps with a fine pen, exactly on the overlap line.
- Unwrap it and measure from the end to the mark with a ruler, in millimetres.
- Type that number into the box above as the circumference.
Things that make the number wrong
- String stretches. Pull it taut to read it and you have added a millimetre. Paper does not stretch — use paper if you have it.
- Thread is too thin. Sewing thread cuts into the skin and reads small. Dental floss or a shoelace is better; a 5 mm paper strip is best.
- Measuring the wrong end of the day. Fingers swell through the day and in the heat. Measure in the evening, with warm hands.
- Measuring the wrong hand. The same finger on the two hands can differ by half a size. Measure the hand the ring will be worn on.
- Forgetting the knuckle. If the knuckle is the widest part, the ring has to clear it. Measure the knuckle too and order the larger of the two.
How to check ring size at home without string
Three substitutes that work, in order of accuracy:
- A strip cut from an envelope or a receipt — anything stiff and thin.
- A thin strip of masking tape wrapped once round the finger, marked and peeled off.
- A ring you already wear: measure the inside diameter across the widest point with a ruler, or match it to a circle on the screen. Do not measure the outside of the band.
What if I am between two sizes?
Half a size is 1.28 mm of circumference, so landing between two is normal rather than a mistake. Take the larger one. A ring that is a touch loose can be sized down cheaply and will still go on over a swollen summer knuckle; a ring that is a touch tight has to come off with soap and is the one people stop wearing.
The exception is a wide band. A 6 mm band wraps more of the finger and sits tighter, so add half a size on top; from 4 mm, add a quarter. The calculator above does this for you when you set the band width.
Measure it twice
Do the whole thing twice, an hour apart, and use the larger reading. Two measurements that agree within a millimetre mean you can order with confidence. Two that are three millimetres apart mean something moved — usually the string was pulled tighter the second time.
For an engagement ring or anything that cannot be resized (eternity bands, tension settings, tungsten, ceramic), have the finger measured on a steel sizer. Home measuring gets you to the right size or the one next to it; a jeweller’s mandrel removes the doubt.
Questions people ask
How can I measure my ring size at home?
Wrap a 5 mm strip of paper round the base of the finger, mark the overlap, unwrap it and measure the length in millimetres with a ruler. That length is the inside circumference — type it into the calculator above and every size follows.
What should I use if I have no string or paper?
Masking tape works, or measure a ring you already wear: lay it flat and read the inside diameter across the widest point. A ring is the most reliable of the three, because it was sized properly in the first place.
Should I measure at the knuckle or at the base of the finger?
Both. The ring sits at the base but has to pass the knuckle. Measure both and order the larger. If the gap is more than a size, ask the jeweller about sizing beads so the ring does not spin.
Why does my size change during the day?
Fingers hold more fluid as the day goes on, and heat, salt, exercise and flights all swell them. The swing across a day is often half a size and can be a full size. Measure in the evening and use that number.
Is a string measurement accurate enough to buy a ring?
Within about a millimetre, which is a third of a size — enough for most purchases. For an eternity band or any setting that cannot be resized, get the finger measured on a steel sizer first.