Measure across the inside
Place the ring flat and measure through its center from one inside edge to the other. A millimeter ruler or suitable caliper helps distinguish small differences. Do not include the outside metal. Repeat the measurement, particularly if the ring is not perfectly round.
Work through an example
For an 18 mm inside diameter, 18 × π is approximately 56.55 mm. If your ruler reads inches, one inch is exactly 25.4 mm. These conversions describe the ring; they do not establish how a wide band will feel or which size a particular seller calls size 8.
Check before ordering
- Use the chart for the chosen variant, not an unrelated conversion image.
- Check the finger and hand you intend to wear it on.
- Consider band width and the seller’s fit guidance.
- Resolve conflicting measurements before buying.
- Check resizing and return options rather than assuming adjustment is possible.
Sources and method
Decalavera’s editorial criteria and examples use AI assistance and documentary checking. References support their specific cultural or technical context; they do not certify products or represent physical tests. Sources from other jurisdictions are not presented as US product certification.
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