Find your ring size, right on the screen.
Match a ring you own against a calibrated circle, or type a measurement, and read the size in US, UK, EU, and Japan — all in your browser.
85.6 × 54 mm
On a phone, the quarter fits the screen better than a card.
Wrap paper or string around the finger, mark the overlap, and measure the length in millimetres.
Three steps, about a minute
Calibrate the screen (optional but exact)
Hold a bank card (or a US quarter on a phone) against the screen and resize the outline until it matches. This fixes the one thing every on-screen sizer gets wrong: how big a millimetre is on your device. Skip it and sizes are still close, just marked approximate.
Match a ring you own
Rest a ring that already fits over the circle and adjust with the slider, the fine buttons, or by dragging the edge until the circle sits just inside the band. No ring handy? Switch tabs and enter a string measurement instead.
Read the size
The readout shows US as the headline, with UK, EU, and Japan plus the inner diameter and circumference in millimetres, so you can double-check against any jeweler's chart.
If the screen isn't ideal
Bright sun, a cracked screen protector, or no ring to copy can all get in the way. These give you the same numbers a different way.
Common questions
How accurate is measuring a ring size on screen?
Without calibration it gives a close ballpark. Calibrate once to a bank card and the on-screen circle matches real millimetres, so a careful measurement lands within about a quarter to a half size. It is a solid estimate for buying, but fingers change through the day and with temperature, so for an engagement ring confirm the final size with a jeweler.
Do I have to calibrate first?
No. The sizer works right away and marks the result approximate. Calibrating takes about ten seconds and makes it exact: hold a standard bank card against the screen and resize the outline until it matches. The tool remembers the calibration on this device.
What if I only have the finger, not a ring?
Switch to the measurement tab and use the string method: wrap a strip of paper or string around the finger, mark where it overlaps, measure that length in millimetres, and enter it. You can also print the paper sizer and wrap the strip around the finger directly.
What is a US size 7 in UK, EU, and Japan?
A US size 7 is about 17.3 mm across the inside (54.4 mm around). That is UK N½, EU 54, and 14 in Japan. The full chart lists every size from 3 to 13.5.
Is it really free, and is my measurement private?
Yes to both. There is no account, no email, and nothing to buy. All of the measuring and converting runs in your browser, so your measurement never leaves the page.
Quick reference
The most-bought sizes at a glance. Thefull chart covers every half size.
| US | Diameter | Circumf. | UK | EU | Japan |
|---|---|---|---|---|---|
| 5 | 15.7 mm | 49.3 mm | J½ | 49 | 9 |
| 6 | 16.5 mm | 51.8 mm | L½ | 52 | 12 |
| 7 | 17.3 mm | 54.4 mm | N½ | 54 | 14 |
| 8 | 18.1 mm | 56.9 mm | P½ | 57 | 16 |
| 9 | 18.9 mm | 59.5 mm | R½ | 59 | 19 |
| 10 | 19.8 mm | 62.0 mm | T½ | 62 | 21 |