Ring Size Converter

Convert ring sizes between US, UK, EU, and Japanese sizing systems. Find your ring size from finger circumference or diameter measurements.

Convert a ring size

Find size from measurement

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How to Measure Your Ring Size

Method 1 — String or paper strip:

Step 1: Cut a thin strip of paper or use a piece of string.

Step 2: Wrap it snugly around the base of the finger you want to measure.

Step 3: Mark where the strip overlaps, then measure the length in millimeters.

Step 4: Enter the measurement in the circumference field above.

Method 2 — Existing ring:

Step 1: Place a ring that fits well on a ruler.

Step 2: Measure the inside diameter in millimeters (the widest point across the opening).

Step 3: Enter the measurement in the diameter field above.

Tips:

  • Measure at the end of the day when your fingers are at their largest.
  • Measure several times for accuracy.
  • Your dominant hand is usually slightly larger.
  • Cold weather makes fingers smaller; warm weather makes them larger.
  • If between two sizes, go with the larger size for comfort.

International Ring Size Chart

US UK EU JP Circ. (mm) Diam. (mm)

Frequently Asked Questions

How do I find my ring size at home?▾
Wrap a thin strip of paper or string around your finger, mark where it overlaps, then measure the length in millimeters. Enter that circumference into the converter to find your size in US, UK, EU, or Japanese sizing.
What is the difference between US and UK ring sizes?▾
US ring sizes use numbers (3-13 with half sizes) while UK sizes use letters (F-Z). For example, a US size 7 equals a UK size N. This converter handles both systems instantly.
How do I convert my ring size to European or Japanese sizing?▾
Enter your known ring size and select the system (US, UK, EU, or JP). The tool instantly shows the equivalent size in all four international systems, plus the circumference and diameter in millimeters.
Is this ring size converter accurate?▾
Yes. The converter uses standardized international ring sizing charts based on ISO, ASTM, British Standard, and JIS specifications. All processing runs in your browser with no signup required.