Use a bank card to calibrate your screen, then measure a paper strip or string to find your US ring size, circumference, and diameter instantly.
Place a real bank card on your screen. Align its top-left corner with the virtual card, then use the slider until the virtual card's left vertical edge matches exactly.
Standard bank card short edge: 53.98 mm. No camera, no upload, no card number needed.
Wrap a thin paper strip or string around the base of your finger, mark the overlap, then flatten it against the screen ruler below.
Keep the strip snug at the finger base. For wide bands, measure twice and consider sizing up by half a size.
If your measurement falls between two sizes, choose the larger size. For wide bands or fingers that swell easily, choose a slightly larger size.
Use this chart as a reference for standard ring size conversions. If your measurement falls between two rows, choose the larger size.
| Circumference mm | Diameter mm | ISO / EU | US / CA | UK / AU | JP / CN | IT / ES / CH | RU |
|---|---|---|---|---|---|---|---|
| 44.2 | 14.1 | 44 | 3 | F | 4 | 4 | 14 |
| 44.8 | 14.3 | 45 | 3.25 | F½ | - | 4⅝ | 14.25 |
| 45.5 | 14.5 | 46 | 3.5 | G | 5 | 5¼ | 14.5 |
| 46.1 | 14.7 | 46 | 3.75 | G½ | 6 | 5⅞ | 14.75 |
| 46.8 | 14.9 | 47 | 4 | H | 7 | 6½ | 15 |
| 47.4 | 15.1 | 47.5 | 4.25 | H½ | - | 7⅛ | - |
| 48.0 | 15.3 | 48 | 4.5 | I | 8 | 7¾ | 15.25 |
| 48.7 | 15.5 | 48.5 | 4.75 | J | - | 8⅜ | 15.5 |
| 49.3 | 15.7 | 49 | 5 | J½ | 9 | 9 | 15.75 |
| 50.0 | 15.9 | 50 | 5.25 | K | - | 9⅝ | 16 |
| 50.6 | 16.1 | 50.5 | 5.5 | K½ | 10 | 10¼ | 16.25 |
| 51.2 | 16.3 | 51 | 5.75 | L | 11 | 10⅞ | - |
| 51.9 | 16.5 | 52 | 6 | L½ | 12 | 11½ | 16.5 |
| 52.5 | 16.7 | 52.5 | 6.25 | M | - | 12⅛ | 16.75 |
| 53.1 | 16.9 | 53 | 6.5 | M½ | 13 | 12¾ | 17 |
| 53.8 | 17.1 | 54 | 6.75 | N | - | 13⅜ | - |
| 54.4 | 17.3 | 54.5 | 7 | N½ | 14 | 14 | 17.25 |
| 55.1 | 17.5 | 55 | 7.25 | O | - | 14⅝ | 17.5 |
| 55.7 | 17.7 | 56 | 7.5 | O½ | 15 | 15¼ | 17.75 |
| 56.3 | 17.9 | 56.5 | 7.75 | P | - | 15⅞ | 18 |
| 57.0 | 18.1 | 57 | 8 | P½ | 16 | 16½ | - |
| 57.6 | 18.3 | 58 | 8.25 | Q | - | 17⅛ | 18.25 |
| 58.3 | 18.6 | 58.5 | 8.5 | Q½ | 17 | 17¾ | 18.5 |
| 58.9 | 18.7 | 59 | 8.75 | R | - | 18⅜ | 18.75 |
| 59.5 | 18.9 | 60 | 9 | R½ | 18 | 19 | 19 |
| 60.2 | 19.2 | 60.5 | 9.25 | S | - | 19⅝ | 19.25 |
| 60.8 | 19.4 | 61 | 9.5 | S½ | 19 | 20¼ | 19.5 |
| 61.4 | 19.5 | 61.5 | 9.75 | T | - | 20⅞ | - |
| 62.1 | 19.8 | 62 | 10 | T½ | 20 | 21½ | 19.75 |
| 62.7 | 20.0 | 63 | 10.25 | U | 21 | 22⅛ | 20 |
| 63.4 | 20.2 | 63.5 | 10.5 | U½ | 22 | 22¾ | - |
| 64.0 | 20.4 | 64 | 10.75 | V | - | 23⅜ | 20.5 |
| 64.6 | 20.6 | 65 | 11 | V½ | 23 | 24 | 20.75 |
| 65.3 | 20.8 | 65.5 | 11.25 | W | - | 24⅝ | - |
| 65.9 | 21.0 | 66 | 11.5 | W½ | 24 | 25¼ | 21 |
| 66.6 | 21.2 | 67 | 11.75 | X | - | 25⅞ | 21.25 |
| 67.2 | 21.4 | 67.5 | 12 | X½ | 25 | 26½ | 21.5 |
| 68.1 | 21.7 | 68 | 12.25 | Y | - | 27⅛ | - |
| 68.5 | 21.8 | 69 | 12.5 | Z | 26 | 27¾ | 21.75 |
| 69.1 | 22.0 | 69.5 | 12.75 | Z½ | - | 28⅜ | - |
| 69.7 | 22.2 | 70 | 13 | - | 27 | 29 | 22 |
To measure ring size at home, wrap a thin paper strip, string, or flexible tape measure around the base of your finger, mark the overlap, then measure the length in millimeters. Use the calculator above to convert the circumference into a recommended US, UK, EU, JP, IT, and RU ring size.
This ring size calculator uses inner circumference in millimeters as the core measurement. Diameter is calculated from circumference, then the buying recommendation rounds up to the next listed ring size instead of rounding down.
Type a circumference or diameter in mm, cm, or inches. The recommendation uses the next larger listed purchase size.
If your measurement falls between two sizes, choose the larger size.
Use a flexible tape measure around the finger base, read the millimeter or inch value, then convert it with the calculator.
Wrap string snugly, mark the overlap, flatten it, and measure the length. Avoid stretchy string because it can make the size too small.
A narrow paper strip is often easier than string because it stays flat and gives a clearer overlap mark.
Measure the inside diameter of a ring that already fits the same finger, then convert diameter to circumference.
Measure the exact finger that will wear the ring. Your ring finger, middle finger, index finger, and pinky can all have different sizes, and knuckle width can change the best fit.
Men's rings are often wider, so a snug measurement may feel tight. For wide bands, measure twice and consider sizing up by half a size.
For engagement rings and thinner bands, measure at normal body temperature and check that the ring can pass comfortably over the knuckle.
Millimeters are the safest input for ring sizing. If you measured in centimeters or inches, convert to millimeters before choosing a ring size.
Wrap paper, string, or a tape measure around the base of your finger, mark the overlap, measure the length, and convert that circumference with the ring size calculator.
Yes. You can use paper, string, a flexible tape measure, or a fitted ring. A calibrated screen ruler helps convert the measurement without a printed ring sizer.
String can work, but paper is often more accurate because it does not stretch. If you use string, keep it snug and measure twice.
Measure the finger circumference in inches, multiply by 25.4 to convert to millimeters, then use the chart or calculator to choose the larger matching size.
Measure the finger circumference in centimeters, multiply by 10 to convert to millimeters, then compare the result with the ring size chart.
The measurement method is the same. Men's average sizes are usually larger and wider bands often need more comfort room, while women's engagement rings are often narrower.
