Questions people actually ask.

Three routes, in order of reliability. If you already own a ring that fits the right finger, lay it on the calibrated circle on screen and match the inside edge — that is the most accurate method available without visiting a jeweller. If you don’t own one, rest the finger itself against the on-screen band and widen the band until it sits snug. If your screen is cracked or strongly curved, print the paper sizer and wrap the strip round the finger instead. Whichever you pick, calibrate the screen against a bank card, a coin or a sheet of paper first: without that step nothing drawn on screen has a known physical size.

Everything you need is already in the house. A bank card, a coin from your own currency, or a sheet of A4 or US Letter sets the scale — all three are standardised, and we hold the published dimensions on file. From there, measure an existing ring’s inside diameter against the screen, or measure the finger directly. If you’d rather stay off the screen entirely, cut a strip of paper about 6 mm wide, wrap it snugly round the base of the finger, mark where it overlaps, and measure to the mark with a ruler — that length is the inside circumference. Avoid string, thread and rubber bands: they stretch, and a stretched loop reads roughly a size large.

The fastest accurate route is a ring that already fits the intended finger. Measure its inside diameter, never the outside — band thickness adds one to three millimetres and inflates the result by a size or more. Set the ring flat on the screen, expand the circle until it just touches the inner edge all the way round, and read the size. One caution: the ring has to genuinely fit. A ring that spins loose, or a heirloom that jams at the knuckle, tells you what that ring measures, not what fits you.

Measure the finger directly. Rest it flat against the on-screen band and widen the band until it sits snug without pressing into the skin — the same light tension a ring you’d actually wear has. Take two or three readings and use the middle one: the bare-finger method carries about ±0.65 of a US size against roughly ±0.4 for measuring an existing ring, so a repeat pass is worth the thirty seconds. Then check the knuckle. If it is noticeably wider than the base of the finger, the ring has to clear it, so size to whichever of the two measurements is larger.

Cut a strip of paper roughly 6 mm wide and 100 mm long — a receipt or an envelope edge works. Wrap it round the base of the finger, snug but not biting, mark where the end overlaps, then lay it flat and measure to the mark in millimetres. That number is your inside circumference: 54 mm is about a US 7, and every 2.55 mm is one full US size. Paper works because it doesn’t stretch. String, thread and elastic do, which is why they routinely come out a size too large.

Measure the exact finger on the exact hand the ring will live on. Fingers on the same hand can differ by a full size, and the dominant hand usually runs about half a size larger than the other. In most of Western Europe and the Americas the engagement and wedding ring sits on the fourth finger of the left hand; in Germany, Russia, India and much of Eastern Europe it sits on the right. If you’re buying a gift and don’t know which applies, measure both fourth fingers and note which is which.

Print at 100%. Turn off “fit to page”, “shrink to fit” and any other scaling option in the print dialog, because they quietly shrink the sheet by two to five percent and shift every size printed on it. Then measure the 50 mm check square on the printed page with a ruler before you cut anything out. If it reads 50 mm the sizer is valid; if it reads 48, reprint rather than trying to compensate in your head. Once verified, cut the strip, thread it through its own slot, and pull it snug round the finger.

Measure twice using two different calibration objects — a bank card and a coin, say — and see whether the results agree. If both land on the same size, you can order with confidence. If they differ by more than half a size, one of the calibrations is off, and redoing the one you trusted less usually settles it. We show a range rather than a single number for exactly this reason: knowing your size means knowing the spread around it, not memorising one digit.

That phrase covers two different jobs. Sizing a ring you already own means having a jeweller cut and rejoin the shank — routine work, usually up to two sizes in either direction, more on a plain band and less on one with stones set round the full circumference. Eternity bands and channel-set rings often cannot be resized at all. Sizing for a ring you are about to buy means measuring first, which is what this tool does. Measure before you buy: it is free, and a resize on a finished ring costs both money and metal.

If you have been given a size — by a jeweller, a retailer, or a ring you bought years ago — verify it against a physical object rather than trusting memory. Measure a ring that currently fits, convert the inside diameter, and compare. Sizes drift: fingers change with age, weight, pregnancy, medication and climate, and a size that was right five years ago can easily be half a size out today. Checking costs a minute.

It depends which system you are being asked for, and a bare number is ambiguous. “Size 7” means a US 7, or 17.3 mm inside diameter — but a Japanese 7 is 15.0 mm, and in the ISO system 7 is not a size at all. The one figure that is unambiguous everywhere is the inside diameter or circumference in millimetres. Measure that once and we convert it into all eleven major national standards at the same time, so you can give a US retailer a US size and a French jeweller a French one without measuring again.

Ring sizing works in millimetres rather than centimetres, because a single centimetre of inside diameter spans more than twelve US sizes — far too coarse to be useful. If your ruler is marked in centimetres, read to the millimetre: a 1.73 cm inside diameter is 17.3 mm, a US 7. To move between the two figures you will see on charts, circumference = diameter × 3.1416, so a 5.4 cm circumference is a 17.2 mm diameter. And measure the inside of the ring, never the outside.

Honestly, you don’t — you estimate, and you accept the error that comes with it. The averages are US 6 to 6.5 for women and US 9 to 10 for men, and roughly two-thirds of adults sit within a size of those. That is fine for a surprise gift that can be exchanged and not fine for a wedding band. Height, shoe size and glove size are not reliable proxies, whatever the charts that use them claim. If you can borrow one ring they already wear, even for two minutes, measure it instead.

A correctly sized ring slides on with light resistance, clears the knuckle without force, and needs a small tug to come back off. If it falls off when your hands are cold it is too big; if you have to twist and pull hard it is too small, and forcing a tight ring risks a swollen, trapped finger. Test late in the day rather than first thing, and check that you can rotate it freely at the base of the finger.

US and Canadian sizes step in halves as standard, and in quarters for finer work — a quarter size is about 0.2 mm of inside diameter. UK sizes step in halves too, written as a letter and a half, like L½. Most mass-market retailers stock whole and half sizes only, so a quarter-size result is best read as a signal for which of the two neighbouring half sizes to order. Bespoke makers will work to a quarter size if you ask.

For a ring you cannot return — a wedding band, anything custom — get sized on a steel mandrel at a jeweller. They slide graduated steel rings onto the finger and read the fit directly, which takes screen calibration out of the equation entirely. It is free at most shops and takes two minutes. Use this tool to know what to expect before you walk in, to sanity-check the number you are given, and for everything you are buying online where a shop visit isn’t practical.

Give the size in their own system, and add the inside diameter in millimetres if there is a notes field. Retailers’ charts are not always identical — some round differently, and some list a “size 7” that is really an ISO 54 — so a millimetre figure removes the ambiguity. Check the returns policy on resizing before you order, and if the band is 6 mm wide or more, tell them the width so they can allow for it.

Lay an existing ring on a flat surface and measure straight across the inside, edge to edge through the centre — that is the inside diameter in millimetres. Finding the true centre line by eye is the hard part, and half a millimetre of error is already more than half a size, so take three readings at different angles and use the largest. If you have only the finger and no ring, wrap a paper strip round it and measure the strip instead: a ruler cannot read a curve.

Look inside the band first. Many rings are stamped with their size next to the metal mark — a number for US sizing, a letter for UK, sometimes a bare “54” for ISO. If the stamp is worn or absent, measure the inside diameter and convert. Be careful with second-hand and inherited rings: a ring that has been resized usually keeps its original stamp, so the number inside can be a size or two away from what it now measures.

With two tools. A ring stick, or mandrel, is a tapered steel cone marked with sizes — an existing ring slides down it until it stops, and the mark at that point is the size. A set of ring gauges is a keyring of graduated steel bands, tried on the finger one at a time until one fits. The mandrel measures rings; the gauges measure fingers. Both are physical standards, which is precisely what an online sizer is calibrating itself towards.

Four steps, about two minutes. One: calibrate the screen by matching the on-screen outline to a bank card, a coin or a sheet of paper. Two: choose whether you are measuring an existing ring or a bare finger. Three: adjust the on-screen circle or band until it matches, viewed square to the screen rather than at an angle — viewing angle is the single most common source of error. Four: read the result, which comes with a confidence range and the equivalent size in every major national system.

Yes — this page is that tool. There is nothing to install and no account to create: you calibrate the screen once against a known object, measure, and the conversion runs entirely in your browser. Expect roughly ±0.4 of a US size when measuring an existing ring and ±0.65 from a bare finger, which is close enough for most purchases and worth confirming at a jeweller for a wedding band. Your calibration is saved in your own device’s storage so you do not have to repeat it.

Yes, and a phone is how most people use this. Two phone-specific notes. First, if you are calibrating with paper, fold an A4 or Letter sheet in half twice so it fits the screen, and tell the sizer you have done so. Second, check that browser zoom is at 100% and that you are not in reader mode or a forced desktop-site view — both change the physical size of a CSS pixel and invalidate the calibration. Screen protectors are fine; a heavily cracked screen is not, so use the printable sizer in that case.

A properly calibrated screen sizer gets you to roughly ±0.4 of a US size when you measure an existing ring, and around ±0.65 when you measure a bare finger. The limit isn’t the maths — it’s physical. At a typical screen density one pixel of misalignment is already about a fifth of a size, and a card held slightly off the flat reads short. We show you the range on every result rather than printing a bare number.

A browser has no way of knowing the physical size of your display. The same image is a different number of millimetres on a phone, a laptop and a 4K monitor. Any sizer that draws a circle without asking you to calibrate first is guessing — and a chart printed at the wrong scale is worse than no chart.

A coin from your own currency works well — pick yours from the list and we use its published diameter. So does a sheet of A4 or US Letter, folded in half twice if you’re on a phone. You can also use a ruler, or let us pre-fill the scale from your device model and confirm it. Card ownership isn’t universal, and a sizer that assumes it isn’t really global.

Yes, and it’s a common cause of wrong sizes elsewhere. Zooming changes the physical size of a CSS pixel, so a calibration done before you zoomed is no longer valid. Our sizer watches for the change and tells you to recalibrate instead of silently handing you a wrong number.

They measure different things. A US size is a position on a scale that steps by exactly 0.8128 mm of inside diameter. A UK size is a letter on a scale that steps by 1.25 mm of circumference. An ISO/EU size simply is the inside circumference in millimetres. Because the steps differ, whole sizes in one system rarely land on whole sizes in another — a US 6 is a British L½, not a round letter.

Borrow a ring they already wear on the right finger and measure its inside diameter — that’s the most reliable route by a wide margin. If you can’t, press one of their rings into a bar of soap or plasticine to capture the inner edge, or trace round the inside on paper. Failing that, compare their finger to your own and measure yours. Average adult sizes are US 6–6.5 for women and US 9–10 for men, but treat that as a fallback, not a plan.

Usually, yes. A wide band contacts more of the finger and wears tighter at the same internal diameter. Below about 4 mm it makes no practical difference. At 6 mm go up about a quarter size; at 8–9 mm about half. Our sizer applies this for you when you set the band width — and it works in the other direction for comfort-fit interiors, which run large.

Go up, in almost every case. A slightly loose ring can be sized down, padded, or fitted with sizing beads. A ring that won’t clear your knuckle is unwearable, and forcing it off risks a trapped finger. The exception is a very wide or very heavy band, where a loose fit will spin and slide — there, favour the snugger size.

Late afternoon or evening, at normal room temperature, when your hands are neither cold nor swollen. Fingers are smallest first thing in the morning and after cold exposure, and largest after heat, salt, exercise or a long flight. Measuring at your daily average gives a ring that fits for most of your waking hours.

Usually. The dominant hand tends to be slightly larger, often by about half a size. Measure the exact finger on the exact hand the ring will live on — and remember that fingers on the same hand differ too.

All eleven of the major national standards: the United States and Canada, the UK and the Wheatsheaf countries, ISO 8653 Europe, France, Germany and the Netherlands, Russia, Italy and Spain and Switzerland, Brazil, Japan, China, and India. Every one is computed from that country’s published definition rather than looked up in a table, so the conversions stay internally consistent.

Your measurement isn’t. The calculation runs entirely in your browser, and your calibration is stored only in your own device’s local storage so you don’t have to redo it — there’s no account and no upload, and no size, finger measurement or calibration value ever reaches us. Like most sites we do count page views, using Google Analytics, which records that a page was opened and can’t see what you measured on it. The privacy policy sets out exactly what that collects and how to switch it off.

Only if you check its scale first. “Fit to page” is on by default in many print dialogs and quietly shrinks the sheet by a few percent, which is enough to shift every size on it by more than a full size. Our printable sizer includes a 50 mm square to measure before you cut anything out.

Size so the ring clears the knuckle, then stop it spinning at the base — sizing beads, a ring guard, or a slightly heavier band all work. A jeweller can fit beads in minutes. Sizing for the base instead means a ring you can’t get on, which is the worse failure.