Wallpapering a room can transform its aesthetic, but accurate measurement is key to avoiding waste and ensuring you have enough material. This calculator helps you determine the number of standard wallpaper rolls required for your project, based on your room dimensions and the specifications of the wallpaper you choose.
How the Calculation Works
The calculator follows these steps:
Calculate Total Wall Area: The perimeter of the room is calculated ((Room Width + Room Depth) * 2), and then multiplied by the Room Height to get the total gross wall area. Note: For simplicity, this calculator assumes a rectangular room and calculates perimeter based on a single width value representing the total length of walls to be papered. If your room has an irregular shape, you'll need to measure and sum the lengths of all wall sections to be wallpapered.
Calculate Area of Obstructions: The area of doors and windows is calculated (Width * Height for each).
Calculate Net Wall Area: The total area of doors and windows is subtracted from the total gross wall area.
Calculate Area per Roll: The area of a single roll of wallpaper is calculated (Wallpaper Roll Width * Wallpaper Roll Length).
Determine Number of Rolls: The Net Wall Area is divided by the Area per Roll. Since you can't buy partial rolls, the result is rounded up to the nearest whole number.
Consider Pattern Repeat (Optional but Recommended): While this calculator doesn't directly factor in pattern repeat (which can significantly increase waste), it's crucial to account for it when purchasing. Always add at least one extra roll if your wallpaper has a large or complex pattern repeat, as you'll lose material aligning the pattern.
Input Explanations:
Room Width (inches): The total linear measurement of all walls you intend to wallpaper. For a standard rectangular room, this would be (Length + Width) * 2.
Room Height (inches): The height from the floor to the ceiling.
Door Width/Height (inches): The dimensions of any doors that will NOT be wallpapered.
Window Width/Height (inches): The dimensions of any windows that will NOT be wallpapered.
Wallpaper Roll Width (inches): The width of a single roll of wallpaper as stated by the manufacturer.
Wallpaper Roll Length (inches): The length of a single roll of wallpaper as stated by the manufacturer.
Example Calculation:
Let's say you have a room with the following dimensions:
Room Width (total perimeter of paperable walls): 500 inches
Room Height: 96 inches
Door Width: 36 inches
Door Height: 84 inches
Window Width: 48 inches
Window Height: 60 inches
Wallpaper Roll Width: 21 inches
Wallpaper Roll Length: 396 inches
Calculation Steps:
Total Wall Area = 500 inches * 96 inches = 48,000 sq inches
Door Area = 36 inches * 84 inches = 3,024 sq inches
Total Obstruction Area = 3,024 + 2,880 = 5,904 sq inches
Net Wall Area = 48,000 – 5,904 = 42,096 sq inches
Area per Roll = 21 inches * 396 inches = 8,316 sq inches
Number of Rolls = 42,096 sq inches / 8,316 sq inches ≈ 5.06 rolls
Rounding up, you would need 6 rolls of wallpaper. It's always wise to buy an extra roll, especially if you are new to wallpapering or if the pattern has a significant repeat.
function calculateWallpaper() {
var roomWidth = parseFloat(document.getElementById("roomWidth").value);
var roomHeight = parseFloat(document.getElementById("roomHeight").value);
var doorWidth = parseFloat(document.getElementById("doorWidth").value);
var doorHeight = parseFloat(document.getElementById("doorHeight").value);
var windowWidth = parseFloat(document.getElementById("windowWidth").value);
var windowHeight = parseFloat(document.getElementById("windowHeight").value);
var wallpaperWidth = parseFloat(document.getElementById("wallpaperWidth").value);
var wallpaperLength = parseFloat(document.getElementById("wallpaperLength").value);
var resultDiv = document.getElementById("result");
var resultSpan = resultDiv.querySelector("span");
// Basic validation
if (isNaN(roomWidth) || roomWidth <= 0 ||
isNaN(roomHeight) || roomHeight <= 0 ||
isNaN(doorWidth) || doorWidth < 0 || // Allow 0 for no door
isNaN(doorHeight) || doorHeight < 0 ||
isNaN(windowWidth) || windowWidth < 0 || // Allow 0 for no window
isNaN(windowHeight) || windowHeight < 0 ||
isNaN(wallpaperWidth) || wallpaperWidth <= 0 ||
isNaN(wallpaperLength) || wallpaperLength <= 0) {
resultSpan.textContent = "Please enter valid numbers.";
resultDiv.style.backgroundColor = "#dc3545"; // Error color
return;
}
// Calculate total wall area
var totalWallArea = roomWidth * roomHeight;
// Calculate obstruction areas
var doorArea = doorWidth * doorHeight;
var windowArea = windowWidth * windowHeight;
var totalObstructionArea = doorArea + windowArea;
// Calculate net wall area
var netWallArea = totalWallArea – totalObstructionArea;
// Ensure net wall area is not negative (in case obstructions are larger than walls)
if (netWallArea 0) {
numberOfRolls = netWallArea / areaPerRoll;
}
// Round up to the nearest whole number as you can't buy partial rolls
var finalRolls = Math.ceil(numberOfRolls);
// Display the result
if (finalRolls === 0 && netWallArea > 0) {
resultSpan.textContent = "Insufficient roll coverage or invalid dimensions.";
resultDiv.style.backgroundColor = "#ffc107″; // Warning color
} else if (finalRolls > 0) {
resultSpan.textContent = finalRolls + " Roll(s)";
resultDiv.style.backgroundColor = "#28a745"; // Success color
} else {
resultSpan.textContent = "0 Rolls Needed";
resultDiv.style.backgroundColor = "#17a2b8"; // Info color
}
}