Inches to Ring Size Converter — US, EU, UK & Japanese Sizes
Measure your finger circumference or diameter in inches and instantly find your US, EU, UK and Japanese ring size. Use a strip of paper or a flexible tape measure for the most accurate circumference reading.
Measurement type
in
- 1
Circumference in mm
2.09 × 25.4 = 53.09 - 2
Raw US size
(53.09 − 36.5) ÷ 2.55 = 6.5043 - 3
US ring size (nearest ½)
round(6.5043 × 2) ÷ 2 = 6.5Rounded to the nearest half-size — the standard increment for US ring sizing.
How does this calculator work?
Wrap a string around your finger and measure it in inches. Multiply by 25.4 for circumference in mm. US size = (mm − 36.5) ÷ 2.55; EU size ≈ circumference in mm. Average women's size is US 6 (≈ 2.04 in / 51.9 mm); average men's is US 10 (≈ 2.45 in / 62.1 mm). Size up if your knuckle is larger than your base.
Formula
How this is calculated
Ring sizes are standardised differently by country. The US sizing system assigns a number where each full size represents approximately 2.55 mm of additional inner circumference, starting from a base offset of 36.5 mm (US size 0). Most adults wear sizes 4–12; women typically 5–8, men typically 7–12.
The EU (ISO) system simply uses the inner circumference in millimetres, so an EU 52 ring has an inner circumference of 52 mm. UK sizes use consecutive letters of the alphabet starting at A (≈ 37 mm inner circumference), with each letter step adding approximately 1.25 mm. Japanese sizes start at a smaller base and use roughly 1.6 mm increments.
For accuracy: measure your finger at the end of the day when it is slightly larger (temperature and salt intake cause swelling). Circumference measurement is more accurate than diameter — wrap a narrow strip of paper or string tightly (but not tight) around the base of the finger, mark where it overlaps, then measure the strip length. If your knuckle is wider than the base, size for the knuckle. All conversion formulas are approximate industry standards; individual brands may vary by ±half a size.
Frequently asked questions
Wrap a thin strip of paper or a piece of string around the base of your ring finger so it fits snugly but can still slide off. Mark the overlap point with a pen, unwrap it, and measure the strip length against a ruler in inches. For greatest accuracy measure at the end of the day and at room temperature.
The average US ring size for women is approximately 6 (inner circumference ≈ 51.9 mm, ≈ 2.04 in), and for men approximately 10 (inner circumference ≈ 62.1 mm, ≈ 2.45 in). These are averages — size varies considerably with hand size and body weight.
They use completely different scales. US sizes are abstract sequential numbers (4, 5, 6…) while EU sizes directly encode the inner circumference in millimetres (EU 52 = 52 mm inner circumference). A US size 6 ≈ EU 51.9 ≈ UK M ≈ JP 12.
Also known as
TG we-Calculate Editorial Team. (2026). Inches to Ring Size Converter — US, EU, UK & Japanese Sizes [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/inches-to-ring-size-converter
TG we-Calculate Editorial Team. "Inches to Ring Size Converter — US, EU, UK & Japanese Sizes." TG we-Calculate. 2026. https://we-calculate.com/calculator/inches-to-ring-size-converter.
TG we-Calculate Editorial Team, "Inches to Ring Size Converter — US, EU, UK & Japanese Sizes," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/inches-to-ring-size-converter
@misc{wecalculate_inches_to_ring_size_converter, title = {Inches to Ring Size Converter — US, EU, UK & Japanese Sizes}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/inches-to-ring-size-converter}}, year = {2026}, note = {TG we-Calculate} }
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