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Ring Size Calculator

Find US ring size from inner diameter.

Calculated Output

US ring size 6.607

Circumference 53.407

Formula: US size ≈ (circumference − 36.5) ÷ 2.55

Step-by-Step Breakdown

1. Values used:

2. Inner diameter = 17

4. US ring size = 6.607

5. Circumference = 53.407

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The math behind it

circumference = π × diameter; US size ≈ (circumference − 36.537) ÷ 2.5535.

17 mm diameter → ~size 6.75.

Measure how?

Measure a well-fitting ring's inner diameter across the middle.