How to use the Ring Size Converter
The ring size converter changes ring sizes between US, UK, EU and Japanese systems.
Open the Ring Size Converter →
The formula
Each system maps to the inside diameter or circumference of the ring.
Worked example
A US size 7 has an inside diameter of about 17.3 mm (circumference about 54.4 mm).
Tips for better results
- Measure a ring that fits you, or your finger, at the end of the day.
- Wider bands may need a half size up.
Common mistakes to avoid
- Measuring when fingers are cold.
- Assuming all brands match the chart.
Please note: Results are estimates for general use. For safety-critical work such as electrical or building projects, check with a qualified professional and local codes. See our Disclaimer.