{
  "slug": "model-railroad-scale",
  "title": "Model Scale Conversion Calculator",
  "heading": "Model Scale Conversion Calculator",
  "category": "math",
  "url": "https://www.revenuelab.fyi/toolbox/model-railroad-scale",
  "summary": "Convert real dimensions to any modeling scale.",
  "description": "HO, N, O, 1:72, 1:35 — enter a prototype dimension and get the scale size in inches and millimeters.",
  "formula": null,
  "dateModified": "2026-09-30",
  "run_url": "https://www.revenuelab.fyi/api/public/calc?tool=model-railroad-scale",
  "inputs": [
    {
      "id": "real",
      "label": "Prototype dimension",
      "kind": "number",
      "hint": null,
      "default": 480,
      "unit": "in",
      "min": null,
      "max": null
    },
    {
      "id": "scale",
      "label": "Scale",
      "kind": "select",
      "hint": null,
      "default": "87.1",
      "options": [
        {
          "value": "160",
          "label": "N (1:160)"
        },
        {
          "value": "87.1",
          "label": "HO (1:87)"
        },
        {
          "value": "76.2",
          "label": "OO (1:76)"
        },
        {
          "value": "72",
          "label": "1:72"
        },
        {
          "value": "48",
          "label": "O (1:48)"
        },
        {
          "value": "35",
          "label": "1:35"
        },
        {
          "value": "24",
          "label": "G (1:24)"
        }
      ]
    }
  ],
  "outputs": [
    {
      "id": "inches",
      "label": "Scale size (in)",
      "format": "decimal",
      "hint": null,
      "primary": true
    },
    {
      "id": "mm",
      "label": "Scale size (mm)",
      "format": "decimal",
      "hint": null,
      "primary": false
    },
    {
      "id": "feet",
      "label": "Scale size (ft)",
      "format": "decimal",
      "hint": null,
      "primary": false
    },
    {
      "id": "ratio",
      "label": "Scale ratio (1:X)",
      "format": "decimal",
      "hint": null,
      "primary": false
    }
  ],
  "worked_example": {
    "inputs": [
      "Prototype dimension: 480 in",
      "Scale: HO (1:87)"
    ],
    "outputs": [
      "Scale size (in): 5.511",
      "Scale size (mm): 139.98",
      "Scale size (ft): 0.459",
      "Scale ratio (1:X): 87.1"
    ]
  },
  "how_to": {
    "title": "How to use this",
    "steps": [
      "Enter prototype dimension (in).",
      "Enter scale.",
      "Read your scale size (in) on the right — it updates as you type.",
      "Hit Share to keep the scenario or send it to someone."
    ]
  },
  "scenarios": [
    {
      "name": "Conservative",
      "description": "Lower-end numbers — what if things land soft?",
      "values": {
        "real": 288,
        "scale": "87.1"
      }
    },
    {
      "name": "Typical",
      "description": "Defaults — the most common real-world setup.",
      "values": {
        "real": 480,
        "scale": "87.1"
      }
    },
    {
      "name": "Ambitious",
      "description": "Higher-end numbers — what if things really pop?",
      "values": {
        "real": 768,
        "scale": "87.1"
      }
    }
  ],
  "limitations": [
    "Results are rounded for display; the underlying calculation keeps full precision.",
    "Very large or very small inputs may hit floating-point limits in the browser.",
    "Inputs outside the accepted range are clamped rather than rejected."
  ],
  "faq": [
    {
      "q": "How does the model scale conversion calculator work?",
      "a": "HO, N, O, 1:72, 1:35 — enter a prototype dimension and get the scale size in inches and millimeters."
    },
    {
      "q": "What do I need to enter?",
      "a": "2 values: prototype dimension, and scale. Each field starts with a sensible default, so you can change one number at a time and watch the result move."
    },
    {
      "q": "What does the scale size (in) result mean?",
      "a": "It is returned as a decimal number and updates live as you edit the inputs, so you can compare two or three versions of a scenario in a few seconds."
    },
    {
      "q": "Is this calculator free, and do I need an account?",
      "a": "Yes, it's free, and no account is required. Nothing you type is stored on our servers — the maths runs entirely in your browser."
    },
    {
      "q": "How accurate is the result?",
      "a": "It applies the standard formula exactly, so the arithmetic is precise. Results are rounded for display; the underlying calculation keeps full precision."
    },
    {
      "q": "Who is this tool for?",
      "a": "It's built for students, developers, and anyone who needs the answer right now without setting up a spreadsheet."
    }
  ],
  "related": [
    "https://www.revenuelab.fyi/toolbox/3d-print-cost"
  ],
  "license": "CC-BY-4.0",
  "citation": "RevenueLab — Model Scale Conversion Calculator (https://www.revenuelab.fyi/toolbox/model-railroad-scale)"
}