How to Find Out Someone's Ring Size Secretly
The most accurate secret method is to borrow a ring they already wear on the same finger of the same hand, and have a jeweler measure it or measure its inside diameter yourself. If you can't take the ring away, trace its inside on paper or press it into soap, or ask a close friend or family member to find out for you.
Method 1: Borrow a ring they already wear
- Pick a ring worn on the finger you are buying for. Fingers on the dominant hand are usually slightly larger.
- Take it to a jeweler, who can size it in moments on a ring mandrel.
- Or measure its inside diameter in millimeters and look it up in the chart below.
- Put it back exactly where you found it.
Method 2: Trace or press the ring
If you only have the ring for a minute, lay it on paper and trace the inside edge with a sharp pencil, or press it halfway into a bar of soap to keep an impression. Measure the inside diameter later. This is less precise than measuring the ring itself, so if you land between two sizes, choose the larger one.
Method 3: Measure the finger while they sleep
Wrap a thin strip of paper around the base of the finger, mark where it overlaps, and measure the length: that is the circumference. It is risky — they may wake up — and string stretches, so use paper and measure twice.
Method 4: Ask an accomplice
A friend can suggest trying on rings during a shopping trip, and a sibling or parent may simply know. This is the only method that doesn't require touching their jewelry.
Method 5: Compare against your own fingers
Slide their ring onto your own fingers and note where it stops. Then measure that spot on your finger. It is rough, but it narrows the range.
Ring size conversion chart
| US / Canada | Circumference (mm) | Inside diameter (mm) | UK / Australia | EU | Japan | China |
|---|---|---|---|---|---|---|
| 4 | 46.8 | 14.9 | H½ | 47 | 7 | 8 |
| 5 | 49.3 | 15.7 | J½ | 49 | 9 | 10 |
| 6 | 51.9 | 16.5 | L½ | 52 | 11 | 12 |
| 7 | 54.4 | 17.3 | N½ | 54 | 14 | 14 |
| 8 | 57.0 | 18.1 | P½ | 57 | 16 | 17 |
| 9 | 59.5 | 18.9 | R½ | 59 | 18 | 19 |
| 10 | 62.1 | 19.8 | T½ | 62 | 20 | 22 |
| 11 | 64.6 | 20.6 | V½ | 64 | 23 | 23 |
Fingers swell in heat and in the evening, and a knuckle can be wider than the base of the finger. If you are unsure, size up: a ring that is slightly large can still be worn and is easier to resize.
Save every finger's size in Sotto
Once you know it, keep it. Sotto stores a ring size for each of the ten fingers, left and right, thumb to pinky, and converts between US, EU, UK, Japanese, Chinese, Hong Kong and Swiss sizes. The size stays private on your phone, ready when the occasion comes.