Apparel SizeRing Size

Diameter (mm) to UK Ring Size for Wide Band Fit

Snapshot

18.1 Ring diameter (mm) equals 9.8 UK ring size. Conversion Encyclopedia uses the same fixed conversion basis across the calculator, common values, and reverse page for this page.

Reference basis: This result uses the selected mm mapping as the profile basis.
Example: For 16.5 Ring diameter (mm), the mm mapping returns 7.9 UK ring size under the same fit assumptions.
Use the reverse page if you need the opposite direction with the same basis.

Use the interactive calculator below for custom values and the common-value table for quick checks.

Interactive conversion

Converter Calculator

9.8 UK value

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Machine access

Available to apps and AI agents

Diameter (mm) to UK Ring Size for Wide Band Fit can be requested through Conversion Encyclopedia's structured interfaces by software and compatible AI agents. The wide-band-fit identifier specifies the fit profile used by the size conversion.

Machine-readable identifiers

Conversion family: ring-size
Source unit: diameter-millimeters
Target unit: uk
Fit: wide-band-fit

The JSON API and OpenAPI specification use the identifiers to reach the conversion engine. WebMCP lets compatible AI agents request the same calculation.

Example API request and response

POST /api/v1/convert

Request

{
  "family": "ring-size",
  "value": 18.1,
  "from": "diameter-millimeters",
  "to": "uk",
  "parameters": {
    "fit": "wide-band-fit"
  }
}

Essential response

{
  "ok": true,
  "conversion": {
    "family": "ring-size",
    "value": 18.1,
    "from": "diameter-millimeters",
    "to": "uk",
    "result": {
      "raw": 9.84251968504,
      "display": "9.8"
    },
    "canonicalPath": "/apparel-size/ring-size/diameter-millimeters-to-uk-for-wide-band-fit/"
  }
}

Full API documentation

Explanation

Diameter (mm) converts to UK by normalizing to ring diameter in millimeters, then remapping to the target system. Fit profile fixed: Wide Band Fit.

From Ring diameter (mm) to UK ring size, results depend on the selected mm fit mapping and stay consistent with that mapping across table rows and calculator input.

Keep the same fit profile in both directions to avoid mixing size mappings that use different apparel allowances.

Method & Size Mapping

Model basis: output depends on the selected fit profile and follows the same fit mapping in both directions.
Profile reference: mm.
Consistency rule: calculator output and table values keep the same fit profile in both directions.

Common Conversion Values

Diameter (mm) value	UK value
16.5	7.9
17.3	8.9
18.1	9.8
19	10.9
20	12.2

Questions & answers

Frequently Asked Questions

Is the reverse ring-size direction available?

Yes. The mirror page UK to Diameter (mm) (Wide Band Fit) uses the inverse path.

Which ring fit profile is used?

Wide Band Fit.

How is Ring diameter (mm) to UK ring size calculated?

The converter applies the formula defined for Ring diameter (mm) to UK ring size, then renders rounded output for the direct answer and common-value rows.