Wallpapering a room can significantly enhance its aesthetic appeal. However, accurately estimating the amount of wallpaper needed is crucial to avoid under- or over-purchasing. This calculator helps you determine the number of wallpaper rolls required based on your room's dimensions and the specifications of the wallpaper you intend to use.
The Math Behind the Calculation
The calculation involves determining the total square footage of the walls to be covered and then dividing that by the square footage of a single wallpaper roll. We also account for common exclusions like doors and windows.
Wall Area Calculation:
The total wall area is calculated by summing the areas of all four walls. For a rectangular room, this is:
2 * (Room Length * Room Height) + 2 * (Room Width * Room Height)
Obstruction Area Calculation:
The areas of doors and windows are subtracted from the total wall area to get the net wall area to be covered.
Door Area = Door Width * Door HeightWindow Area = Window Width * Window HeightTotal Obstruction Area = (2 * Door Area) + (2 * Window Area)
(Note: This assumes two doors and two windows for simplicity in a standard room calculation. Adjustments may be needed for rooms with more or fewer openings.)
Net Wall Area:Net Wall Area = Total Wall Area - Total Obstruction Area
Wallpaper Roll Area:
The area covered by a single roll of wallpaper is:
Wallpaper Roll Area = Wallpaper Roll Width * Wallpaper Roll Length
Number of Rolls:
The total number of rolls needed is calculated by dividing the Net Wall Area by the Wallpaper Roll Area. Since you can't buy fractions of a roll, we always round up to the nearest whole number.
Number of Rolls = Ceiling(Net Wall Area / Wallpaper Roll Area)
Important Considerations:
Pattern Repeat: Many wallpapers have a pattern repeat, meaning you'll need to align specific sections of the pattern. This often requires purchasing extra wallpaper to account for waste. The calculator provides a base estimate; always check the wallpaper manufacturer's recommendations for pattern repeat and add an extra roll if significant pattern matching is required.
Waste: Even without a pattern repeat, cutting and fitting wallpaper will result in some waste. It's generally recommended to add 10-15% extra to your calculated amount. This calculator does not automatically add this percentage, so consider it when making your final purchase.
Room Shape: This calculator assumes a standard rectangular room. For rooms with alcoves, angled walls, or complex architectural features, manual adjustments or more detailed calculations will be necessary.
Units: Ensure all measurements are in the same units (feet in this calculator) for accurate results.
When to Use This Calculator:
This calculator is ideal for homeowners, DIY enthusiasts, and professional decorators planning to wallpaper any room, including bedrooms, living rooms, dining rooms, hallways, and even accent walls. It simplifies the often-confusing task of estimating wallpaper quantities, helping you budget effectively and ensure you have enough material to complete your project smoothly.
function calculateWallpaper() {
var roomHeight = parseFloat(document.getElementById("roomHeight").value);
var roomWidth = parseFloat(document.getElementById("roomWidth").value);
var roomLength = parseFloat(document.getElementById("roomLength").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 wallpaperRollWidth = parseFloat(document.getElementById("wallpaperRollWidth").value);
var wallpaperRollLength = parseFloat(document.getElementById("wallpaperRollLength").value);
var resultElement = document.getElementById("result-value");
resultElement.innerText = "–"; // Reset previous result
// Validate inputs
if (isNaN(roomHeight) || roomHeight <= 0 ||
isNaN(roomWidth) || roomWidth <= 0 ||
isNaN(roomLength) || roomLength <= 0 ||
isNaN(doorWidth) || doorWidth < 0 || // Doors/windows can be 0
isNaN(doorHeight) || doorHeight < 0 ||
isNaN(windowWidth) || windowWidth < 0 ||
isNaN(windowHeight) || windowHeight < 0 ||
isNaN(wallpaperRollWidth) || wallpaperRollWidth <= 0 ||
isNaN(wallpaperRollLength) || wallpaperRollLength <= 0) {
alert("Please enter valid positive numbers for all dimensions.");
return;
}
// Calculate total wall area
var wallArea = 2 * (roomLength * roomHeight) + 2 * (roomWidth * roomHeight);
// Calculate obstruction areas
var doorArea = doorWidth * doorHeight;
var windowArea = windowWidth * windowHeight;
var totalObstructionArea = doorArea + windowArea; // Assuming one door and one window for simplicity in this basic calculator
// Calculate net wall area
var netWallArea = wallArea – totalObstructionArea;
// Ensure net wall area is not negative
if (netWallArea 0) {
numberOfRolls = netWallArea / wallpaperRollArea;
}
// Round up to the nearest whole number
var finalRollsNeeded = Math.ceil(numberOfRolls);
resultElement.innerText = finalRollsNeeded;
}