{
  "id": "drywall",
  "version": "1bb94acbed83",
  "status": "published",
  "name": "Drywall Calculator",
  "question": "How much drywall should I buy?",
  "summary": "Computes how many sheets of drywall (sheetrock, gypsum board) cover a room’s walls, and its ceiling if chosen, less doors and windows, with an extra share for waste.",
  "category": "construction",
  "subcategory": "materials",
  "url": "https://www.acalculator.org/construction/drywall-calculator",
  "markdown": "https://www.acalculator.org/construction/drywall-calculator.md",
  "kind": "function",
  "method": "Area = 2 × (length + width) × height − doors × door area − windows × window area (+ length × width for the ceiling); sheets = area × (1 + extra ÷ 100) ÷ sheet area, rounded up.",
  "assumptions": [
    "The room is a rectangle with walls of one height; door and window openings are not covered.",
    "By default a door opening is 20 ft² (36 × 80 in) and a window 15 ft² (3 × 5 ft).",
    "Extra for waste is 10% by default, for cut-offs around openings and at wall ends.",
    "Sheets are counted by area; the count does not plan where each seam falls."
  ],
  "inputs": {
    "$schema": "https://json-schema.org/draft/2020-12/schema",
    "type": "object",
    "properties": {
      "l": {
        "title": "Room length",
        "description": "The length of the room, wall to wall.",
        "type": [
          "number",
          "string"
        ],
        "x-quantity": "length",
        "exclusiveMinimum": 0,
        "maximum": 1000
      },
      "w": {
        "title": "Room width",
        "description": "The width of the room, wall to wall.",
        "type": [
          "number",
          "string"
        ],
        "x-quantity": "length",
        "exclusiveMinimum": 0,
        "maximum": 1000
      },
      "h": {
        "title": "Wall height",
        "description": "The height of the walls, floor to ceiling.",
        "type": [
          "number",
          "string"
        ],
        "x-quantity": "length",
        "exclusiveMinimum": 0,
        "maximum": 1000
      },
      "sheet": {
        "title": "Sheet size",
        "description": "The size of one drywall sheet.",
        "type": "string",
        "enum": [
          "4x8",
          "4x9",
          "4x10",
          "4x12",
          "54x12",
          "1200x2400",
          "1200x2700"
        ]
      },
      "extra": {
        "title": "Extra for waste",
        "description": "Drywall to add, in percent, for cut-offs around openings and at the ends of walls.",
        "type": "number",
        "x-unit": "percent",
        "minimum": 0,
        "maximum": 100
      },
      "doors": {
        "title": "Doors",
        "description": "How many doors are in the walls.",
        "type": "integer",
        "minimum": 0,
        "maximum": 100
      },
      "da": {
        "title": "Area of one door",
        "description": "The area of one door opening: 20 ft² for 36 × 80 in.",
        "type": [
          "number",
          "string"
        ],
        "x-quantity": "area",
        "minimum": 0,
        "maximum": 10000
      },
      "win": {
        "title": "Windows",
        "description": "How many windows are in the walls.",
        "type": "integer",
        "minimum": 0,
        "maximum": 100
      },
      "wa": {
        "title": "Area of one window",
        "description": "The area of one window opening: 15 ft² for 3 × 5 ft.",
        "type": [
          "number",
          "string"
        ],
        "x-quantity": "area",
        "minimum": 0,
        "maximum": 10000
      },
      "ceil": {
        "title": "Cover the ceiling too",
        "description": "Whether to add the ceiling (length × width) to the area.",
        "type": "boolean"
      }
    }
  },
  "outputs": {
    "sheets": {
      "label": "Sheets to buy",
      "description": "The area with extra ÷ the area of one sheet, rounded up to whole sheets.",
      "format": "integer"
    },
    "exactSheets": {
      "label": "Sheets, not rounded",
      "description": "The area with extra ÷ the area of one sheet, before rounding up.",
      "format": "number"
    },
    "squareFeet": {
      "label": "Area to cover, ft²",
      "description": "The wall area less doors and windows, plus the ceiling if chosen, before the extra.",
      "format": "number"
    },
    "squareMeters": {
      "label": "Area to cover, m²",
      "description": "The same area in square metres.",
      "format": "number"
    }
  },
  "defaultAnswer": {
    "inputs": {
      "l": 3.6576000000000004,
      "w": 4.2672,
      "h": 2.4384,
      "sheet": "4x8",
      "extra": 10,
      "doors": 1,
      "da": 1.8580608,
      "win": 2,
      "wa": 1.3935456000000002,
      "ceil": false
    },
    "outputs": {
      "sheets": 13,
      "exactSheets": 12.58125,
      "squareFeet": 366,
      "squareMeters": 34.00251264
    },
    "text": "For 366 ft² of drywall, the sheets to buy come to 13 (12.58 before rounding up)."
  },
  "examples": [
    {
      "given": {
        "l": 3.6576000000000004,
        "w": 4.2672,
        "h": 2.4384,
        "sheet": "4x8",
        "extra": 10,
        "doors": 1,
        "da": 1.8580608,
        "win": 2,
        "wa": 1.3935456000000002,
        "ceil": false
      },
      "expect": {
        "squareFeet": 366,
        "exactSheets": 12.58125,
        "sheets": 13
      },
      "source": "NIST Handbook 44, Appendix C (1 ft = 0.3048 m); hand calculation in content.mdx: 2 × 26 × 8 − 50 = 366 ft² × 1.1 ÷ 32 = 12.58, so 13 sheets"
    },
    {
      "given": {
        "l": 3.6576000000000004,
        "w": 3.6576000000000004,
        "h": 2.4384,
        "sheet": "4x12",
        "extra": 0,
        "doors": 0,
        "da": 1.8580608,
        "win": 0,
        "wa": 1.3935456000000002,
        "ceil": true
      },
      "expect": {
        "squareFeet": 528,
        "exactSheets": 11,
        "sheets": 11
      },
      "source": "Hand calculation in content.mdx: 2 × 24 × 8 + 144 = 528 ft² ÷ 48 = 11 sheets (NIST Handbook 44 units)"
    },
    {
      "given": {
        "l": 4,
        "w": 3,
        "h": 2.5,
        "sheet": "1200x2400",
        "extra": 10,
        "doors": 1,
        "da": 1.8,
        "win": 1,
        "wa": 1.5,
        "ceil": false
      },
      "expect": {
        "squareMeters": 31.7,
        "exactSheets": 12.10763888888889,
        "sheets": 13
      },
      "source": "Hand calculation in content.mdx: 2 × 7 × 2.5 − 1.8 − 1.5 = 31.7 m² × 1.1 ÷ 2.88 = 12.11, so 13 sheets (NIST Handbook 44 units)"
    }
  ],
  "sources": [
    "NIST Handbook 44 (2024), Appendix C, General Tables of Units of Measurement: 1 ft = 12 in = 0.3048 m; 1 ft² = 144 in². https://www.nist.gov/pml/owm/nist-handbook-44-current-edition",
    "OpenStax, Prealgebra 2e, §9.4 Use Properties of Rectangles, Triangles, and Trapezoids (area and perimeter of a rectangle). https://openstax.org/books/prealgebra-2e/pages/9-4-use-properties-of-rectangles-triangles-and-trapezoids"
  ],
  "related": [
    "paint",
    "square-footage"
  ],
  "changelog": [
    {
      "date": "2026-09-30",
      "note": "The answer names the area in m² in Metric."
    }
  ]
}