{
  "schemaVersion": 1,
  "slug": "watch-size-calculator",
  "category": "fashion",
  "kind": "implementation",
  "independentValidation": false,
  "implementationHash": "a63aece3bb7cb69c1063147961a8f556767562c303f8c7690db895e663605dda",
  "provenance": "Generated from the calculation contract used by the published page. Publication is not external validation.",
  "sourceFiles": [
    "data/calculators/watch-size-calculator.json",
    "src/engine.js"
  ],
  "runtimeSource": "/sources/engine.txt",
  "runtimeHash": "5c888d8898afbdee36267bb9977829e1e2ac568f6677c8ee87469c139864645c",
  "scope": "The compute function records implemented equations, constants, lookup tables and custom rules. Inputs record defaults and allowed values; outputs record precision and units. Defaults are examples, not recommendations. General background references are not evidence for this specific algorithm.",
  "publishedFormula": {
    "formula": "D = wrist_mm × 0.24 × style_factor; lug = round_even(D÷2); thickness = 0.28D; range = D ± 2 mm",
    "vars": [
      [
        "wrist_mm",
        "Wrist circumference (mm)"
      ],
      [
        "style_factor",
        "Dress 0.94, sport 1.00, diver 1.08"
      ],
      [
        "D",
        "Estimated case diameter (mm)"
      ]
    ],
    "note": "Style factor: dress 0.94, sport 1.00, diver 1.08. These are planning assumptions, not a fit or comfort guarantee."
  },
  "externalEvidence": {
    "reviewedAt": "2026-10-12",
    "sources": [
      {
        "name": "Tissot — Wrist measurement and bracelet length",
        "url": "https://www.tissotwatches.com/en-gb/sizeguide"
      }
    ],
    "referenceRole": "input",
    "implementationHash": "a63aece3bb7cb69c1063147961a8f556767562c303f8c7690db895e663605dda",
    "basis": "D = wrist_mm × 0.24 × style_factor; lug = round_even(D÷2); thickness = 0.28D; range = D ± 2 mm",
    "limitations": "Use the cited guidance and your own measurements, bills or product specifications to choose inputs. Sample defaults are not current local data."
  },
  "contract": {
    "compute": "const wmm = (unit === 'cm' ? wrist : wrist*2.54)*10; const base = wmm*0.24; const factor = style === 'dress' ? 0.94 : style === 'diver' ? 1.08 : 1; const dia = base*factor; const lug = Math.round(dia*0.5/2)*2; return { caseDiameter: dia, caseMmRange: Math.round(dia - 2) + '–' + Math.round(dia + 2), lugWidth: lug, thickness: dia*0.28, wristMm: wmm };",
    "inputs": [
      {
        "name": "wrist",
        "type": "number",
        "default": 6.5,
        "min": 4,
        "max": 12,
        "step": 0.1,
        "unitField": "unit",
        "minByUnit": {
          "in": 4,
          "cm": 10.16
        },
        "maxByUnit": {
          "in": 12,
          "cm": 30.48
        },
        "unitScales": {
          "in": 1,
          "cm": 0.39370078740157477
        }
      },
      {
        "name": "unit",
        "type": "select",
        "default": "in",
        "options": [
          {
            "value": "in"
          },
          {
            "value": "cm"
          }
        ]
      },
      {
        "name": "style",
        "type": "select",
        "default": "dress",
        "options": [
          {
            "value": "dress"
          },
          {
            "value": "sport"
          },
          {
            "value": "diver"
          }
        ]
      }
    ],
    "outputs": [
      {
        "name": "caseDiameter",
        "precision": 1,
        "unit": "mm"
      },
      {
        "name": "caseMmRange",
        "precision": 0,
        "unit": "",
        "type": "text"
      },
      {
        "name": "lugWidth",
        "precision": 0,
        "unit": "mm"
      },
      {
        "name": "thickness",
        "precision": 1,
        "unit": "mm"
      },
      {
        "name": "wristMm",
        "precision": 0,
        "unit": "mm"
      }
    ],
    "interpret": null
  }
}