Ring sizes use different systems across countries. Use the chart supplied for the specific ring and check whether its measurements refer to inner diameter or circumference.
Use the right reference
A ring that fits the intended finger can be a useful comparison if you can measure it accurately. A wide band may feel different from a narrow one in the same nominal size.
Avoid guessing from a photograph
Perspective and screen size distort proportions. If the size chart or measurement method is unclear, ask for clarification before ordering.
Finger size can change during the day. Compare measurements at more than one time and follow the seller’s sizing instructions. Check the adjustment or return options before purchasing.