{
  "id": "floor-area-ratio",
  "version": "6e031b7e408c",
  "status": "published",
  "name": "Floor Area Ratio Calculator",
  "question": "What is the floor area ratio?",
  "summary": "Computes the floor area ratio (FAR) of a building from its total floor area and the lot area, or the floor area a FAR allows on a lot.",
  "category": "construction",
  "subcategory": "materials",
  "url": "https://www.acalculator.org/construction/floor-area-ratio-calculator",
  "markdown": "https://www.acalculator.org/construction/floor-area-ratio-calculator.md",
  "kind": "formulas",
  "method": "FAR = total floor area ÷ lot area; floor area = FAR × lot area; lot area = floor area ÷ FAR.",
  "assumptions": [
    "The floor area is the total the zoning code counts: many codes leave out cellars, mechanical space and some parking.",
    "Both areas are in the same unit; the ratio has no unit."
  ],
  "inputs": {
    "$schema": "https://json-schema.org/draft/2020-12/schema",
    "type": "object",
    "properties": {
      "floor": {
        "title": "Total floor area",
        "description": "The floor area of every story of every building on the lot, added up, as the zoning code counts it.",
        "type": [
          "number",
          "string"
        ],
        "x-quantity": "area",
        "exclusiveMinimum": 0,
        "maximum": 1000000000
      },
      "lot": {
        "title": "Lot area",
        "description": "The area of the lot (the zoning lot).",
        "type": [
          "number",
          "string"
        ],
        "x-quantity": "area",
        "exclusiveMinimum": 0,
        "maximum": 1000000000
      },
      "far": {
        "title": "Floor area ratio (FAR)",
        "description": "The total floor area divided by the lot area.",
        "type": "number",
        "exclusiveMinimum": 0,
        "maximum": 1000
      }
    }
  },
  "solve": {
    "fillAny": 2,
    "variables": [
      "floor",
      "lot",
      "far"
    ],
    "inputsOnly": []
  },
  "outputs": {
    "floorArea": {
      "label": "Total floor area",
      "description": "The floor area of every story of every building on the lot, added up, as the zoning code counts it.",
      "format": "quantity"
    },
    "lotArea": {
      "label": "Lot area",
      "description": "The area of the lot (the zoning lot).",
      "format": "quantity"
    },
    "far": {
      "label": "Floor area ratio",
      "description": "The total floor area divided by the lot area.",
      "format": "number"
    }
  },
  "defaultAnswer": {
    "inputs": {
      "lot": 929.0304000000001,
      "floor": 1858.0608000000002
    },
    "outputs": {
      "far": 2
    },
    "text": "A floor area of 20,000 ft² on a lot of 10,000 ft² is a floor area ratio of 2."
  },
  "examples": [
    {
      "given": {
        "lot": 929.0304000000001,
        "floor": 1858.0608000000002
      },
      "expect": {
        "far": 2
      },
      "source": "NYC Zoning Resolution §12-10, definition of floor area ratio (a 10,000 ft² lot with 20,000 ft² of floor area has a FAR of 2.0; a 20,000 ft² lot with 40,000 ft² of floor area also has 2.0), https://zr.planning.nyc.gov/article-i/chapter-2/12-10 (retrieved 2026-10-18)"
    },
    {
      "given": {
        "lot": 1858.0608000000002,
        "floor": 3716.1216000000004
      },
      "expect": {
        "far": 2
      },
      "source": "NYC Zoning Resolution §12-10, definition of floor area ratio (a 10,000 ft² lot with 20,000 ft² of floor area has a FAR of 2.0; a 20,000 ft² lot with 40,000 ft² of floor area also has 2.0), https://zr.planning.nyc.gov/article-i/chapter-2/12-10 (retrieved 2026-10-18)"
    },
    {
      "given": {
        "lot": 464.51520000000005,
        "far": 0.5
      },
      "expect": {
        "floor": 232.25760000000002
      },
      "source": "hand calculation in content.mdx: 0.5 × 5,000 = 2,500 ft²; NYC Zoning Resolution §12-10, definition of floor area ratio (a 10,000 ft² lot with 20,000 ft² of floor area has a FAR of 2.0; a 20,000 ft² lot with 40,000 ft² of floor area also has 2.0), https://zr.planning.nyc.gov/article-i/chapter-2/12-10 (retrieved 2026-10-18)"
    },
    {
      "given": {
        "floor": 3000,
        "far": 1.5
      },
      "expect": {
        "lot": 2000
      },
      "source": "hand calculation in content.mdx: 3,000 ÷ 1.5 = 2,000 m²"
    }
  ],
  "sources": [
    "NYC Zoning Resolution, Section 12-10 Definitions: \"floor area ratio\" (total floor area on a zoning lot divided by the lot area, with worked examples), \"floor area\" (and what it leaves out) and \"lot coverage\". https://zr.planning.nyc.gov/article-i/chapter-2/12-10 (retrieved 2026-10-18)",
    "NIST SP 811 (2008), Appendix B: 1 ft = 0.3048 m exactly, so 1 ft² = 0.09290304 m². https://www.nist.gov/pml/special-publication-811 (retrieved 2026-10-18)",
    "NIST, U.S. Survey Foot: Revised Unit Conversion Factors: 1 acre = 43,560 ft² = 4,046.856 422 4 m² with the international foot; units based on the U.S. survey foot are to be avoided after December 31, 2022. https://www.nist.gov/pml/us-surveyfoot/revised-unit-conversion-factors (retrieved 2026-10-18)"
  ],
  "related": [
    "square-footage",
    "acreage"
  ],
  "changelog": []
}