{
  "id": "wallpaper",
  "version": "948d803bbc05",
  "status": "published",
  "name": "Wallpaper Calculator",
  "question": "How much wallpaper do I need?",
  "summary": "Works out how many rolls of wallpaper a room needs from its size, the roll width and length, and the pattern repeat, by counting the strips each roll gives.",
  "category": "construction",
  "subcategory": "materials",
  "url": "https://www.acalculator.org/construction/wallpaper-calculator",
  "markdown": "https://www.acalculator.org/construction/wallpaper-calculator.md",
  "kind": "function",
  "method": "Strips = ⌈2 × (length + width) ÷ roll width⌉; strip length = wall height rounded up to whole repeats; strips per roll = ⌊roll length ÷ strip length⌋; rolls = max(1, ⌈strips ÷ strips per roll⌉ − ⌊doors and windows ÷ 4⌋) + spare rolls.",
  "assumptions": [
    "The room is a rectangle and every wall is papered to the same height.",
    "Each strip starts at the same point of the pattern, so it is the wall height rounded up to whole repeats; leftover paper on a roll shorter than a strip is waste.",
    "Every 4 ordinary-size doors or windows save one roll (Brewster’s rule); larger openings are not deducted.",
    "One spare roll by default, as Cole & Son advise, for matching and mistakes. Buy all rolls from the same batch (dye lot)."
  ],
  "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",
        "minimum": 0.01,
        "maximum": 1000
      },
      "w": {
        "title": "Room width",
        "description": "The width of the room, wall to wall.",
        "type": [
          "number",
          "string"
        ],
        "x-quantity": "length",
        "minimum": 0.01,
        "maximum": 1000
      },
      "h": {
        "title": "Wall height",
        "description": "The height to paper, floor (or baseboard) to ceiling.",
        "type": [
          "number",
          "string"
        ],
        "x-quantity": "length",
        "minimum": 0.01,
        "maximum": 1000
      },
      "rw": {
        "title": "Roll width",
        "description": "The width of the paper on the roll: 20.5 in on most US rolls.",
        "type": [
          "number",
          "string"
        ],
        "x-quantity": "length",
        "minimum": 0.01,
        "maximum": 1000
      },
      "rl": {
        "title": "Roll length",
        "description": "The length of paper on one roll: 33 ft on a US double roll.",
        "type": [
          "number",
          "string"
        ],
        "x-quantity": "length",
        "minimum": 0.01,
        "maximum": 1000
      },
      "rep": {
        "title": "Pattern repeat",
        "description": "The height of one repeat of the pattern; 0 for a free match or plain paper.",
        "type": [
          "number",
          "string"
        ],
        "x-quantity": "length",
        "minimum": 0,
        "maximum": 1000
      },
      "open": {
        "title": "Doors and windows",
        "description": "How many ordinary-size doors and windows the walls have; every 4 save one roll.",
        "type": "integer",
        "minimum": 0,
        "maximum": 100
      },
      "spare": {
        "title": "Spare rolls",
        "description": "Extra rolls for pattern matching, mistakes and later repairs.",
        "type": "integer",
        "minimum": 0,
        "maximum": 100
      },
      "p": {
        "title": "Price per roll",
        "description": "Optional: what one roll costs, to total the cost.",
        "type": "number",
        "x-unit": "USD",
        "minimum": 0,
        "maximum": 1000000
      }
    }
  },
  "outputs": {
    "rolls": {
      "label": "Rolls to buy",
      "description": "The rolls for the strips, less one per 4 doors or windows, plus the spare rolls.",
      "format": "integer"
    },
    "strips": {
      "label": "Strips (drops)",
      "description": "The room perimeter ÷ the roll width, rounded up.",
      "format": "integer"
    },
    "drop": {
      "label": "Length of each strip",
      "description": "The wall height, rounded up to whole pattern repeats.",
      "format": "quantity",
      "unit": "ft"
    },
    "perRoll": {
      "label": "Strips per roll",
      "description": "How many whole strips one roll gives: roll length ÷ strip length, rounded down.",
      "format": "integer"
    },
    "area": {
      "label": "Wall area",
      "description": "The room perimeter × the wall height, with no deduction for doors or windows.",
      "format": "quantity",
      "unit": "ft2"
    },
    "cost": {
      "label": "Total cost",
      "description": "Rolls to buy × the price per roll.",
      "format": "money"
    }
  },
  "defaultAnswer": {
    "inputs": {
      "l": 3.6576000000000004,
      "w": 3.6576000000000004,
      "h": 2.4384,
      "rw": 0.5206999999999999,
      "rl": 10.0584,
      "rep": 0,
      "open": 2,
      "spare": 1
    },
    "outputs": {
      "rolls": 9,
      "strips": 29,
      "drop": 2.4384,
      "perRoll": 4,
      "area": 35.674767360000004
    },
    "text": "A 12 ft × 12 ft room with 8 ft walls needs 9 rolls (29 strips, 4 per roll)."
  },
  "examples": [
    {
      "given": {
        "l": 3.6576000000000004,
        "w": 3.6576000000000004,
        "h": 2.4384,
        "rw": 0.5206999999999999,
        "rl": 10.0584,
        "rep": 0,
        "open": 2,
        "spare": 1
      },
      "expect": {
        "strips": 29,
        "perRoll": 4,
        "rolls": 9,
        "area": 35.674767360000004
      },
      "source": "Brewster Wallcovering, Wallpaper Calculator (1 bolt = 56 ft², 20.5 in × 33 ft; deduct 1 bolt for every 4 ordinary doors or windows), https://www.brewsterwallcovering.com/wallpaper-calculator, retrieved 2026-10-02; Cole & Son, Wallpaper Calculator (add an extra roll for pattern matching and waste), https://cole-and-son.com/pages/wallpaper-calculator, retrieved 2026-10-02; hand calculation in content.mdx: 576 in ÷ 20.5 in = 28.1, so 29 strips; 33 ÷ 8 = 4.1, so 4 a roll; 29 ÷ 4 = 7.25, so 8 rolls, + 1 spare = 9",
      "tolerance": 1e-12
    },
    {
      "given": {
        "l": 4.2672,
        "w": 3.048,
        "h": 2.7432000000000003,
        "rw": 0.5206999999999999,
        "rl": 10.0584,
        "rep": 0.5334,
        "open": 4,
        "spare": 1,
        "p": 60
      },
      "expect": {
        "strips": 29,
        "drop": 3.2003999999999997,
        "perRoll": 3,
        "rolls": 10,
        "cost": 600
      },
      "source": "Brewster Wallcovering, Wallpaper Calculator (1 bolt = 56 ft², 20.5 in × 33 ft; deduct 1 bolt for every 4 ordinary doors or windows), https://www.brewsterwallcovering.com/wallpaper-calculator, retrieved 2026-10-02; Cole & Son, Wallpaper Calculator (add an extra roll for pattern matching and waste), https://cole-and-son.com/pages/wallpaper-calculator, retrieved 2026-10-02; hand calculation in content.mdx: 108 in ÷ 21 in = 5.14, so 6 repeats = 126 in; 396 ÷ 126 = 3.1, so 3 a roll; 29 ÷ 3 = 9.67, so 10 rolls, − 1 for 4 openings, + 1 spare = 10",
      "tolerance": 1e-12
    },
    {
      "given": {
        "l": 4,
        "w": 3,
        "h": 2.5,
        "rw": 0.53,
        "rl": 10.05,
        "rep": 0.64,
        "open": 0,
        "spare": 0
      },
      "expect": {
        "strips": 27,
        "drop": 2.56,
        "perRoll": 3,
        "rolls": 9
      },
      "source": "hand calculation in content.mdx: 14 m ÷ 0.53 m = 26.4, so 27 strips; 2.5 ÷ 0.64 = 3.9, so 4 repeats = 2.56 m; 10.05 ÷ 2.56 = 3.9, so 3 a roll; 27 ÷ 3 = 9 rolls",
      "tolerance": 1e-12
    },
    {
      "given": {
        "l": 6.2484,
        "w": 6.2484,
        "h": 2.4384,
        "rw": 0.5206999999999999,
        "rl": 10.0584,
        "rep": 0,
        "open": 0,
        "spare": 0
      },
      "expect": {
        "strips": 48,
        "rolls": 12
      },
      "source": "hand calculation in content.mdx: 2 × (20.5 + 20.5) ft = 82 ft = 984 in = 48 × 20.5 in exactly"
    }
  ],
  "sources": [
    "Brewster Wallcovering, Wallpaper Calculator (1 bolt = 56 ft², 20.5 in × 33 ft; deduct 1 bolt for every 4 ordinary-size doors or windows; larger repeats need more rolls), retrieved 2026-10-02. https://www.brewsterwallcovering.com/wallpaper-calculator",
    "Cole & Son, Estimate How Many Rolls of Wallpaper You Will Need (add an extra roll for pattern matching and waste), retrieved 2026-10-02. https://cole-and-son.com/pages/wallpaper-calculator",
    "Milton & King, How Many Wallpaper Rolls Do I Need? (rolls 2 ft × 32.9 ft; measure each wall; doors and windows count as waste), retrieved 2026-10-02. https://www.miltonandking.com/blog/how-many-wallpaper-rolls-do-i-need-how-to-measure-the-room/"
  ],
  "related": [
    "paint",
    "drywall",
    "square-footage"
  ],
  "changelog": []
}