Skip to main content

Ring Size Converter

Unit Converters

Circumference/diameter to HK, US, EU and JP sizes

Quick Answer

Ring Size Converter: Circumference/diameter to HK, US, EU and JP sizes. HK (China): size = C − 38 · EU/ISO: size = C.

Measure the finger circumference with a strip of paper at the intended ring position (evening, warm hands). EU size = circumference in mm; HK size ≈ EU − 40.
HK size (common in China)HK 16
US size7
EU/ISO size54
JP size14
Inner diameter17.2mm
Circumference 54.0 mm matches US 7 / EU 54. Between sizes? Choose the larger one for wide bands, the smaller for thin bands.

Calculation steps

  1. 1Measured circumference: 54.0 mm
  2. 2Inner diameter = circumference ÷ π = 54.0 ÷ 3.14159 = 17.2 mm
  3. 3Nearest ISO 8653 row 54 mm → HK 16 / US 7 / EU 54 / JP 14

ISO 8653 size chart

Circ. (mm)EUUSHKJP
44.244364
46.847497
49.3495119
51.95261411
54.45471614
575781816
59.56092018
62.162102320
64.665112523
67.267122725
69.770133027
Measure in the evening with warm hands — fingers swell in summer and shrink in cold. EU size equals the inner circumference in millimetres (ISO 8653); mainland China jewellers mostly use HK size (≈ EU − 40), so confirm which system a shop uses before ordering online.

Was this tool helpful?

How to Use

  1. Pick units: switch source and target units in the Ring Size Converter.
  2. Enter a value: results sync both ways instantly — no convert button needed.
  3. Use the reference table: common conversions are listed for instant lookup.
  4. Copy the result: copy the converted value with its unit.

Key Points

  • Ring Size Converter is a free online unit conversion tool — open and use, no sign-up.
  • All calculations run locally in your browser; your data never leaves the device.
  • Key capability: Circumference/diameter to HK, US, EU and JP sizes.
  • Results come with formulas and reference tables so you can verify every number.

Formula & How It Works

Ring size systems (inner circumference C in mm)

HK (China): size = C − 38 · EU/ISO: size = C
US: size ≈ (C − 36.5) ÷ 2.55 · JP: ≈ (diameter − 11.2) ÷ 0.317 + 1
C = π × diameter

FAQ

How do I use the Ring Size Converter?
Open the page and fill in the input fields — results update automatically. Circumference/diameter to HK, US, EU and JP sizes.
Are the results accurate?
Yes. Standard formulas and conversion factors are used and verified.
Is it free? Do I need to sign up?
Completely free. No registration, login or download required.
Does it work on mobile?
Yes. The responsive design works on phones, tablets and desktops.
Is my data saved?
No. Everything runs locally in your browser.

Related Tools

Related Guides

Source & Updates

Based on SI conversion factors and international standards. Last updated: 2025-07

Authoritative sources:

Last updated:

Formulas and content on this page are reviewed by the YiJianSuan team. For reference only — official sources prevail.

Maintained and periodically reviewed by the YiJianSuan editorial team — review process in ourEditorial Policy.

Cite this page: YiJianSuan. Ring Size Converter[EB/OL]. https://www.yijiansuan.com/en/c/convert/ring-size

Results provided by this tool are for reference only and do not constitute professional advice.