A free online ring size calculator for converting between US, UK, EU, and Japanese ring sizing systems. Enter finger circumference or diameter in millimeters, or input a known size in any system. Includes a complete size chart with 24 sizes from US 3 to US 15, with circumference and diameter for each.
Choose input method: circumference, diameter, or known size.
Enter your measurement or known size.
View converted sizes across all systems.
Reference the full size chart.
Use a piece of string or paper to wrap around your finger, mark where it meets, and measure the length in millimeters for the circumference.
The most common ring sizes are US 6-8 for women and US 9-11 for men.
Free online tool — works in your browser, no sign-up required. Start using it right now.
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