Find your ring size at home
Find your ring size on screen: match the outline to a bank card, lay a ring on the circle and read the size. A ring 17.3 mm across inside is US 7, UK N½ and ISO 54. Nothing is uploaded; the measurement stays in your browser.
- Match the outline to your bank card
- Lay your ring on the circle
- Read your size in every system
Match the outline to a bank card
Hold a bank card flat against the screen, short edge up, with its sides on the dashed lines. Slide until the outline and the card are the same width, then confirm.
Lay your ring on the circle
Put a ring that fits flat on the circle. Slide until the circle touches the inside edge of the ring all the way round.
Your ring size
17.3 mm across is US 7, UK N½ and ISO 54.
Inside circumference: 54.4 mm · Inside diameter: 17.3 mm
| System | Size | Match |
|---|---|---|
| US and Canada | 7 | exact |
| UK and Australia | N½ | exact |
| ISO / Europe | 54 | closest: −0.4 mm |
| Switzerland, Italy, Spain | 14 | closest: −0.4 mm |
| Japan | 14 | exact |
| Hong Kong and China | 15 | exact |
| India | 14 | closest: −0.4 mm |
Expected accuracy: about ±0.3 mm of inside diameter if the card was matched carefully. This is an estimate from the geometry, not a measurement on many devices.
Check the scale with a coin
Lay a coin on the screen and compare it with its circle. If the edges do not meet, match the card again.
How the on-screen sizer works
A screen does not tell a web page how big a millimetre is, so the sizer asks you to match an outline to something you can measure: the short edge of a bank card, 53.98 mm. From that it knows how many screen pixels make a millimetre and draws the circle at the real size.
Then you lay a ring that fits flat on the circle and move the slider until the circle meets the ring’s inside edge. The inside edge matters, not the outside: it is the inside diameter that sets the size.
Pinching to zoom or changing the browser zoom changes the scale. The page notices and asks you to match the card again. A coin check at the bottom shows whether the scale is right.
What it can and cannot do
The on-screen sizer is the least precise way to find a ring size, because it depends on how closely you match the card edge and the ring edge. Done carefully it is usually within about half a US size, which is our estimate from the geometry, not a measurement on many devices.
For a ring you cannot return, check the result with the printable sizer, which is drawn at true scale, or ask a jeweller to size the finger.
Questions
How accurate is an on-screen ring sizer?
About 0.3 mm of inside diameter when you match the card carefully, which is under half a US size. It is an estimate from the geometry, so use the printable sizer or a jeweller before an expensive purchase.
Why does the sizer use a bank card?
Every bank card is 85.60 by 53.98 mm (ISO/IEC 7810 ID-1), so it is a known length you already own. The sizer uses the short edge, 53.98 mm, because it fits across any phone screen.
What if I do not have a ring that fits?
Measure the finger with a paper strip and use the converter, or print the sizer. The page on how to measure a ring size explains each method.
Does the site keep my measurement?
No. The calibration is saved only in your own browser, so you do not have to match the card each visit. Nothing about your ring or finger is sent to the site.