A ring already worn on that finger is the surest measure.
Rest it flat on a bank card, keep the whole card in frame, and photograph it from directly above. The card measures 85.60 mm along its long edge, which gives the image its scale. Attach the photograph below and the reading is confirmed at the bench, before the gold is drawn.
A wide band sits closer than a thin one.
A setting of this depth covers more of the finger, so the upper of two readings is the one to choose. Measure at the end of the day, when the hand is at its widest: a warm hand and a cold hand read two sizes apart.
Sizes run from 44 to 66
| Europe | US | UK | Ø mm |
| 44 | 3 | F½ | 14.0 |
| 46 | 3¾ | H | 14.6 |
| 48 | 4½ | I½ | 15.3 |
| 50 | 5¼ | K | 15.9 |
| 52 | 6 | L½ | 16.6 |
| 54 | 6¾ | N | 17.2 |
| 56 | 7¾ | P | 17.8 |
| 58 | 8½ | Q½ | 18.5 |
| 60 | 9¼ | S | 19.1 |
| 62 | 10 | T½ | 19.7 |
| 64 | 10¾ | V | 20.4 |
| 66 | 11½ | W½ | 21.0 |