Calibration
Five ways to calibrate, not one.
Card sizers assume everyone carries a bank card. Pick a coin from your own currency, fold a sheet of A4, use a ruler, or let us pre-fill the scale from your device — then confirm it.
Free ring size calculator · No sign-up
Find your ring size. Then know how accurate it is.
A free ring size calculator that measures to a tenth of a millimetre. Calibrate your screen against something real — a bank card, a coin from your own currency, a folded sheet of paper — then read your size in every country’s ring size chart, with an honest accuracy range around it.
- 11 national standards
- Accuracy range on every result
- Your measurements stay in your browser
Virtual ring sizer
- 1Calibrate
- 2Measure
- 3Result
Your screen scale changed. Page zoom or a display change happened after you calibrated, so the measurement below is no longer to scale.
Calibrate your screen
Your browser has no idea how big your screen physically is. Match one real object and every measurement after this is true to size.
Most accurate. Works worldwide.
Drag the slider, or focus it and use the arrow keys for single-pixel steps. Hold the object flat against the screen — a tilted card reads small.
Screen scale: — CSS pixels per mm
Verify with a second object
Optional, and the single best thing you can do for accuracy. Calibrate again with something different — if the two agree, your scale is proven rather than assumed.
Measure
Four ways in, depending on what you have to hand. Measuring a ring that already fits is by far the most reliable.
Most accurate. Match a ring that already fits.
Your size
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Refine the fit
Measurement is only half of it. These are the factors a jeweller adjusts for — each one moves the number, and shows you by how much.
Your size everywhere
Every value below is computed from your measurement, not looked up in a table. Send a jeweller the millimetres if you want to remove all doubt.
| Region | Your size | What the number means |
|---|
Why this one
Most on-screen sizers stop at “here’s a number.”
A ring that is half a size out still doesn’t fit. The difference between a good sizer and a bad one is not the circle on the screen — it’s everything around it.
Verification
Prove the scale, don’t assume it.
Calibrate a second time with a different object. If the two agree, your screen scale is verified and we say so. If they disagree, we tell you that too, instead of quietly picking one.
Honesty
Every result carries its error bar.
A number with no tolerance is a guess wearing a suit. We state the accuracy range alongside your size, and which part of the process is limiting it.
Fit model
Band width and knuckles are arithmetic here.
Wide bands wear tighter. Comfort-fit interiors run large. Knuckles need clearance. Other sizers print these as tips; we compute them and show you exactly how much each one moved your size.
Coverage
Genuinely global, not just four countries.
All 11 national standards, from the ISO circumference used across Europe to Japan’s JIS scale, Brazil’s NBR 16058 and the letter sizes used from Dublin to Auckland.
Method
Formulas, not a typed-out table.
Every size is derived from the published standard at the moment you ask for it. Hand-keyed charts drift and pick up typos — we found a duplicated size in a competitor’s chart while researching this one.
Straight answer
No screen sizer is perfect. Here’s what actually limits it.
At a typical screen density, a single pixel of misalignment is already about a fifth of a US size. Add a card held at a slight angle, or the parallax from looking at the screen off-axis, and you have the real error floor — and it is not in the arithmetic.
So we attack the parts that can be fixed. Multiple calibration references that check each other. Sub-pixel adjustment with the arrow keys. Detection when page zoom silently invalidates your scale. And a stated tolerance, so you know whether to order or to double-check.
For a ring you cannot return, or a proposal you cannot redo, get sized on a steel mandrel at a jeweller. Use this to know what to expect before you walk in, and to buy with confidence everywhere else.
Ring size guide
Everything the number above doesn’t tell you.
Most people arrive here with one question — what ring size am I? — and leave with three more: which country’s scale is that, how sure can I be, and will the ring still fit in August. This is the short version of the answer. The ring size calculator above does the arithmetic; the sections below cover how to measure ring size accurately, how to read the result, and when to distrust it.
How to measure your ring size at home
There are four ways to measure ring size at home, and they are not equal. Measuring a ring that already fits is the most accurate, because a ring has a hard circular edge and hard edges are easy to align against. A paper strip wrapped around the finger comes second — paper doesn’t stretch, which is exactly why it beats string or thread. A printable ring size chart is third, and only if you verify the print scale first. Measuring a bare finger against the screen comes last: fingers are oval rather than round and soft tissue compresses, so treat that number as a starting point and confirm it another way. The full guide ranks all four.
How to find your ring size without a ring to measure
If you’re sizing for a surprise, borrow a ring they already wear on the correct finger and measure its inside diameter — that is by far the most reliable route to how to find your ring size for someone else. Failing that, press one of their rings into a bar of soap or plasticine to capture the inner edge, or trace round the inside on paper and measure the circle. Comparing their hand against your own and measuring yours is a distant fourth, but it still beats guessing. Whichever route you take, the calculator states how much confidence the method earns.
How to read a ring size chart
A ring size chart looks like a straight translation table, but the systems measure genuinely different things. A US size is a position on a scale stepping 0.8128 mm of inside diameter at a time. A British size is a letter stepping 1.25 mm of circumference. An ISO or European size simply is the inside circumference in millimetres — a size 52 ring measures 52 mm around the inside. Because the step sizes don’t line up, whole sizes in one system rarely land on whole sizes in another, which is why every conversion here is shown with its ring size measurements in millimetres beside it.
Average ring size for women and men
The average ring size for women is around a US 6 to 6.5, and a mens ring size chart centres on a US 9 to 10 — roughly 16.5 mm and 18.9 mm of inside diameter respectively. Treat those as a fallback for a gift you genuinely cannot measure for, not as a plan. Hand size varies far more than the averages suggest, the dominant hand usually runs about half a size larger than the other, and a wide band on an otherwise average finger can still need a quarter size more than the bare measurement.
A ring size app with nothing to install
People search for a ring size app expecting a download. This is one, minus the install: it runs in your browser, keeps working offline once the page has loaded, and every measurement stays on your own device — nothing is uploaded and there is no account. The one thing no app can escape is calibration. A browser has no way of knowing how physically large your screen is, so you match one real object first, and every measurement after that is true to scale.
When to print a ring sizer instead
On a phone with a cracked or strongly curved screen, or when you want something physical to hand to someone else, use the printable ring size chart. It carries a 50 mm check square, because “fit to page” quietly shrinks a sheet by a few percent and shifts every size printed on it. And for a ring you cannot return, get sized on a steel mandrel at a jeweller — use this to know what to expect before you walk in, and to buy with confidence everywhere else.
Ring Size Chart
Conversion chart
A complete ring size chart with international conversions: US, UK, ISO/EU, France, Germany, Russia, Italy, Brazil, Japan, China and India, plus mm diameter.
Learn
How to Measure
How to measure your ring size at home: the paper strip method, measuring a ring that fits, and screen calibration — ranked by accuracy, with what shifts your size.
Printable Sizer
Printable sizer
A free printable ring size chart and paper ring sizer, with a print-scale check square so a page your printer shrank can’t hand you the wrong ring size.
Company
Who’s behind this, and what happens to your data.
About Us
Who builds this, how every size is derived from a published standard, and how a free tool with no ads pays for itself.
Contact Us
Questions, feature requests, or a correction to a size chart. We read every message and reply to the address you give us.
Privacy Policy
No accounts and no advertising. What the sizer saves on your device, what our page-view analytics sees, and the one place you can hand us anything.
Terms & Conditions
What you may do with the charts and the printable sizer, and the honest limits of an on-screen measurement.