{
    "name": "Wallpaper Roll Count Calculator",
    "url": "https://calculators.geekmidst.com/calculators/wallpaper-roll-count-calculator",
    "markdown": "https://calculators.geekmidst.com/calculators/wallpaper-roll-count-calculator.md",
    "category": "Construction",
    "description": "Count the wallpaper rolls a room needs from wall width and height, roll size and pattern repeat, using the drops-per-roll method decorators use.",
    "summary": "Work out how many full-height drops each roll gives, allowing for pattern repeat and trimming, then how many drops go round the room. Rolls = drops ÷ drops per roll, rounded up.",
    "also_called": [
        "Wallpaper estimator"
    ],
    "applies_to": "Worldwide",
    "last_updated": "2026-10-29",
    "computation": "Results are computed in the visitor’s browser on the HTML page. This API describes the calculator; it does not compute results.",
    "inputs": [
        {
            "name": "perimeter",
            "label": "Total width of walls to paper",
            "type": "number",
            "default": "14",
            "unit": "m"
        },
        {
            "name": "height",
            "label": "Wall height",
            "type": "number",
            "default": "2.4",
            "unit": "m"
        },
        {
            "name": "openings",
            "label": "Width of full-height openings to skip",
            "type": "number",
            "default": "0",
            "unit": "m",
            "optional": true
        },
        {
            "name": "roll_width",
            "label": "Roll width",
            "type": "number",
            "default": "0.53",
            "unit": "m"
        },
        {
            "name": "roll_length",
            "label": "Roll length",
            "type": "number",
            "default": "10.05",
            "unit": "m"
        },
        {
            "name": "repeat",
            "label": "Pattern repeat",
            "type": "number",
            "default": "0",
            "unit": "cm",
            "optional": true
        },
        {
            "name": "trim",
            "label": "Trim allowance per drop",
            "type": "number",
            "default": "10",
            "unit": "cm"
        },
        {
            "name": "spare_rolls",
            "label": "Spare rolls",
            "type": "number",
            "default": "0",
            "optional": true
        }
    ],
    "outputs": [
        {
            "key": "rolls",
            "label": "Rolls to buy",
            "format": "integer"
        },
        {
            "key": "strips",
            "label": "Drops needed",
            "format": "integer"
        },
        {
            "key": "drops_per_roll",
            "label": "Drops per roll",
            "format": "integer"
        },
        {
            "key": "drop_length",
            "label": "Cut length per drop",
            "format": "number"
        }
    ],
    "formula": {
        "text": "Drop = Height + Repeat + Trim;  Drops per roll = ⌊Roll length ÷ Drop⌋;  Drops = ⌈(Wall width − Openings) ÷ Roll width⌉;  Rolls = ⌈Drops ÷ Drops per roll⌉ + spares",
        "variables": {
            "Repeat": "vertical pattern repeat",
            "Trim": "allowance for trimming top and bottom"
        }
    },
    "worked_example": {
        "inputs": {
            "perimeter": "14",
            "height": "2.4",
            "openings": "0",
            "roll_width": "0.53",
            "roll_length": "10.05",
            "repeat": "0",
            "trim": "10",
            "spare_rolls": "0"
        },
        "steps": [
            "Drop = 2.4 + 0 + 0.1 = 2.5 m, so ⌊10.05 ÷ 2.5⌋ = 4 drops per roll.",
            "Drops = ⌈14 ÷ 0.53⌉ = 27.",
            "Rolls = ⌈27 ÷ 4⌉ = 7."
        ],
        "result": "Walls 14 m round and 2.4 m high need 7 rolls of 0.53 × 10.05 m plain wallpaper."
    },
    "interpretation": "Buy all rolls from the same batch number so the shade matches, and keep a spare in case of damage.",
    "assumptions": [
        "Adding a full repeat to each drop is a safe allowance for pattern matching."
    ],
    "limitations": [
        "Offset (drop) patterns can waste more; ceilings and sloping walls are not handled."
    ],
    "rules": null,
    "faqs": [
        {
            "question": "Why subtract only full-height openings?",
            "answer": "Above and below ordinary windows you still need drops, so their width usually saves little paper."
        },
        {
            "question": "What is a pattern repeat?",
            "answer": "The vertical distance before the pattern repeats. Each drop must start at the same point in the pattern, which wastes up to one repeat per drop."
        }
    ],
    "sources": [],
    "related": [
        {
            "name": "Ceiling Panel Count Calculator",
            "url": "https://calculators.geekmidst.com/calculators/ceiling-panel-count-calculator"
        },
        {
            "name": "Adhesive Coverage Calculator",
            "url": "https://calculators.geekmidst.com/calculators/adhesive-coverage-calculator"
        },
        {
            "name": "Carpet Roll Quantity Calculator",
            "url": "https://calculators.geekmidst.com/calculators/carpet-roll-quantity-calculator"
        }
    ],
    "disclaimer": "Quantities are estimates. Confirm requirements with your engineer or supplier before ordering materials.",
    "publisher": "GM¹X CalcVerse"
}