How to measure ring size at home

Five methods work at home, in this order of accuracy: measure the inside diameter of a ring that already fits, use a printable ring sizer at 100% scale, wrap a 6 mm paper strip around the finger and measure to the overlap mark, match your ring on a calibrated on-screen sizer, or read the finger width against a millimetre ruler. Look the millimetres up in the ring size chart to get a US, UK, EU, Indian or Japanese size.

Your ring size is a name for one measurement: the inside circumference of the band, in millimetres. Measure that — or the inside diameter, multiplied by 3.1416 — and every national size follows from it. US size = (circumference in mm − 36.537) ÷ 2.5535, so 51.9 mm is a US 6 and 62.1 mm is a US 10.

Lay the ring flat, measure straight across the inside hole at its widest point in millimetres, and use the inside edge of the band rather than the outside. A caliper is ideal; a steel ruler read at eye level is close enough. That diameter maps to a size directly — 16.5 mm is a US 6, 19.8 mm a US 10.

Use the paper strip method. Cut a strip about 6 mm wide, wrap it snugly round the base of the finger, mark where it overlaps, then lay it flat and measure to the mark. That length is your circumference in millimetres. Check the strip passes over your knuckle before you trust the number.

Measure exactly as you would in millimetres, then divide by 10 — ring sizing is defined in millimetres, so centimetres are only a rescaling. A US 6 is 5.19 cm around the inside and 1.65 cm across; a US 10 is 6.21 cm around and 1.98 cm across. One full US size is only 0.26 cm of circumference, so read to two decimal places or measure in millimetres instead.

You cannot know it, only estimate it. Most women order between US 5 and 7, with 6 to 6.5 the average ring size for women; most men order between US 8 and 12, with 10 the most common size on the men’s ring size chart. Treat that as a placeholder for a surprise gift, and buy from a jeweller who resizes free.

Borrow a ring they already wear on the right finger and measure its inside diameter, or press it into a bar of soap and measure the impression. Failing that, compare their finger against your own, or ask someone who has shopped for them before. Note which finger and which hand — the dominant hand runs a quarter to half a size larger.

Measure twice on different days, ideally by two different methods. Readings within about 1 mm of each other mean you can trust the result; a wider gap means something moved — a stretched paper strip, an uncalibrated screen, or a cold hand. Confirming a screen measurement against a printed sizer is the quickest cross-check.

Two ways. Best: lay a ring that already fits on the ruler and read the inside diameter in millimetres. Rougher: press the finger flat against the ruler, read its width at the base, and add about 6% to allow for the flattening. The finger method is good to roughly one size, so use it to sanity-check rather than to order.

Take your measurement to the chart, not the chart to your finger. Find your inside diameter or circumference in millimetres in the international ring size chart and read across for the US number, UK letter, EU/ISO number and the Indian and Japanese equivalents. If your figure falls between two rows, take the larger one.

A jeweller resizes gold, silver and platinum bands about two sizes either way, by cutting the shank and adding or removing metal. Tungsten, titanium, ceramic and full eternity bands generally cannot be resized and have to be replaced. For a ring that is only slightly loose, a sizing bead or a plastic ring guard is cheaper and reversible.

No. The dominant hand is usually a quarter to half a size larger, and fingers differ within a hand — the index and middle finger are rarely the same. Measure the exact finger on the exact hand the ring will be worn on.

Yes. A wide band presses along the length of the finger, so the same nominal size wears tighter. Add roughly half a size from about 5 mm of width and a full size from about 9 mm — the band width table above lists the allowances, and the calculator applies them once you measure the band.

Measuring an existing ring with a caliper is within about ±0.1 mm. A printed sizer checked against a bank card, or a card-calibrated screen, lands within roughly ±0.15 to ±0.3 mm — about a fifth to two fifths of a US size, and the accuracy page shows how those bounds are derived. The paper strip is good to about half a size, a ruler against the finger to about one size. A jeweller’s steel mandrel stays the reference standard for an expensive ring.

Late afternoon or evening, at room temperature. Fingers are smallest when cold and first thing in the morning, and swell in heat, after exercise and after a salty meal. Sizing at your largest means the ring fits all day rather than only part of it.

Measure both and choose a size between the two — nearer the knuckle measurement, so the ring goes on, but not so loose that it spins. A comfort-fit band, domed on the inside edge, passes a large knuckle more easily at the same size.

Round up. A ring that is slightly large can be resized, beaded or guarded; one that will not pass the knuckle cannot be worn at all while you wait for an exchange.

Yes, once the screen is calibrated. A CSS pixel has no fixed physical width, so the on-screen sizer first asks you to match a bank card, pick your device, or enter your screen diagonal. After that it draws true millimetres, and you lay the ring flat on the glass to read the size.