Find your ring size on screen
Calibrate with any bank card, lay a ring on the screen and get US, UK, EU and Japan sizes.
Ring size tool
- 1 Calibrate
- 2 Measure
- 3 Your size
Step 1 · Calibrate
Hold a card on the outline and slide until they match.
Use 100% browser zoom and turn off page zoom first.
Step 2 · Measure
Calibrated ✓ ·
Place the ring here; match the inner edge
17.3 mm
Step 3 · Your size
US 7
Between sizes? Choose the larger. It is easier to wear and easier to adjust.
Open full converterSave my size
Optional. Nothing is sent to us.
Screens are only exact after calibration. Treat the result as a close guide, and check with a jeweler before ordering an important ring.
- Card calibration
- Works on phone & desktop
- US · UK · EU · JP
How it works
Three steps
Calibrate
Hold a bank card to the screen and match the outline. The tool now knows your screen’s real millimetres.
Measure
Lay a ring that fits flat on the circle and adjust until the circle matches its inner edge.
Read your size
See the size in US, UK, EU and Japan, then open the converter or save it on this device.
Buying a gift
Gift tips
- Borrow a ring she or he already wears on the same finger, and measure it while they are out.
- Press a ring into a bar of soap to keep its size, then measure the print.
- Ask a close friend or family member, who may already know the size.
- Fingers swell in warmth and in the evening. If unsure, choose the larger size.
- Buying a wide band? Wide rings feel tighter than thin ones at the same size. If the ring is wider than about 4–5 mm, tell the jeweler, who may suggest a slightly larger size.
- The two hands are not always the same size, so measure a ring from the hand and finger it will be worn on.
Questions
FAQ
How accurate is the screen ring sizer?
After calibration with a bank card, the circle on your screen matches real millimetres. How close you get depends on how carefully you line up the inner edge, so measure two or three times and compare. For an engagement ring, double-check with a jeweler, who can measure with metal finger gauges.
Why do I need a bank card?
Every screen shows pixels at a different size. All bank cards are the same width (85.60 mm, set by ISO/IEC 7810 ID-1), so matching one tells the tool how many pixels make a millimetre.
Do you store my size?
Only if you press “Save on this device”. It is then kept in your own browser (localStorage). We have no accounts and send nothing to a server.
Should I measure the inside or outside of the ring?
The inside. Match the gold circle to the inner edge of the ring, where it touches the finger.
What if the size is between two sizes?
Choose the larger size. A ring that is slightly loose is more comfortable than one that will not go over the knuckle, and it is usually easier for a jeweler to make a ring smaller than larger. Some designs, such as full eternity rings, can be hard to resize at all, so ask before you buy.
How we calculate
How we calculate: the EU size is the inner circumference in millimetres, as defined in ISO 8653:2016. US sizes follow the US scale where each whole size adds 0.032 in (0.8128 mm) to the inner diameter, so diameter = 11.63 mm + 0.8128 mm × US size. UK letters follow British Standard 6820:1987 (size C = 40 mm circumference, each letter adds 1.25 mm). Japanese sizes come from the equivalency table on Wikipedia (Japanese sizes are whole numbers that do not follow a straight formula, so they are rounded to the nearest size). Sources: ISO 8653:2016, Ring size (Wikipedia), equivalency table, Larson Jewelers conversion chart. Charts from different jewelers can round slightly differently, so for an important ring check with the jeweler.