function updateUnits() {
var units = document.getElementById('units').value;
var lengthLabels = document.getElementsByClassName('unit-length');
var areaLabels = document.getElementsByClassName('unit-area');
if (units === 'metric') {
for (var i = 0; i < lengthLabels.length; i++) {
lengthLabels[i].textContent = 'm';
}
for (var j = 0; j < areaLabels.length; j++) {
areaLabels[j].textContent = 'cm';
}
document.getElementById('wallHeight').placeholder = 'e.g., 2.5';
document.getElementById('wallWidth').placeholder = 'e.g., 4';
document.getElementById('rollLength').placeholder = 'e.g., 10';
document.getElementById('rollWidth').placeholder = 'e.g., 52';
document.getElementById('patternRepeat').placeholder = 'e.g., 64';
} else {
for (var k = 0; k < lengthLabels.length; k++) {
lengthLabels[k].textContent = 'ft';
}
for (var l = 0; l < areaLabels.length; l++) {
areaLabels[l].textContent = 'in';
}
document.getElementById('wallHeight').placeholder = 'e.g., 8';
document.getElementById('wallWidth').placeholder = 'e.g., 12';
document.getElementById('rollLength').placeholder = 'e.g., 33';
document.getElementById('rollWidth').placeholder = 'e.g., 20.5';
document.getElementById('patternRepeat').placeholder = 'e.g., 21';
}
}
function calculateWallpaper() {
var units = document.getElementById('units').value;
var wallHeight = parseFloat(document.getElementById('wallHeight').value);
var wallWidth = parseFloat(document.getElementById('wallWidth').value);
var rollLength = parseFloat(document.getElementById('rollLength').value);
var rollWidth = parseFloat(document.getElementById('rollWidth').value);
var patternRepeat = parseFloat(document.getElementById('patternRepeat').value);
var addContingency = document.getElementById('addContingency').checked;
var resultDiv = document.getElementById('wallpaperResult');
if (isNaN(wallHeight) || isNaN(wallWidth) || isNaN(rollLength) || isNaN(rollWidth) || isNaN(patternRepeat)) {
resultDiv.innerHTML = "Please enter valid numbers in all fields.";
return;
}
if (wallHeight <= 0 || wallWidth <= 0 || rollLength <= 0 || rollWidth <= 0) {
resultDiv.innerHTML = "Measurements must be greater than zero.";
return;
}
var wallHeightCm, wallWidthCm, rollLengthCm, rollWidthCm, patternRepeatCm;
if (units === 'metric') {
wallHeightCm = wallHeight * 100;
wallWidthCm = wallWidth * 100;
rollLengthCm = rollLength * 100;
rollWidthCm = rollWidth;
patternRepeatCm = patternRepeat;
} else { // Imperial
wallHeightCm = wallHeight * 30.48;
wallWidthCm = wallWidth * 30.48;
rollLengthCm = rollLength * 30.48;
rollWidthCm = rollWidth * 2.54;
patternRepeatCm = patternRepeat * 2.54;
}
if (patternRepeatCm 0) {
var repeatsPerDrop = Math.ceil((wallHeightCm + trimAllowance) / patternRepeatCm);
cutLengthPerDrop = repeatsPerDrop * patternRepeatCm;
} else {
cutLengthPerDrop = wallHeightCm + trimAllowance;
}
if (cutLengthPerDrop > rollLengthCm) {
resultDiv.innerHTML = "The required drop length (" + (cutLengthPerDrop/100).toFixed(2) + " m) is longer than the roll length. Please check your measurements.";
return;
}
// Calculate how many full drops you can get from one roll
var dropsPerRoll = Math.floor(rollLengthCm / cutLengthPerDrop);
if (dropsPerRoll === 0) {
resultDiv.innerHTML = "Cannot get a single drop from a roll. Please check your measurements.";
return;
}
// Calculate the total number of rolls needed
var totalRolls = Math.ceil(dropsNeeded / dropsPerRoll);
// Add contingency if checked
if (addContingency) {
totalRolls = Math.ceil(totalRolls * 1.1);
}
resultDiv.innerHTML = "You will need " + totalRolls + " roll(s) of wallpaper."
+ "Calculation Details:"
+ "Strips (Drops) Needed: " + dropsNeeded + ""
+ "Usable Drops Per Roll: " + dropsPerRoll + "";
}
// Initialize units on page load
document.addEventListener('DOMContentLoaded', function() {
updateUnits();
});
Creating a stunning feature wall with wallpaper can transform a room, but buying the right amount is crucial. Too little, and you risk running out mid-project with no guarantee of finding a matching batch. Too much, and you've wasted money. Our Feature Wall Wallpaper Calculator takes the guesswork out of the process, ensuring you get it right the first time.
How to Measure Your Feature Wall
Accuracy is key. Follow these simple steps for perfect measurements:
Wall Height: Measure from the top of your skirting board to the ceiling (or cornice). Take this measurement in three different places—left, middle, and right—and use the largest of the three values in the calculator. Walls are rarely perfectly straight.
Wall Width: Measure the horizontal width of the wall from corner to corner. Again, measure at the top, middle, and bottom, and use the largest measurement. Do not subtract for windows or doors unless they are exceptionally large, as this area is often needed for pattern matching wastage.
Understanding Wallpaper Roll Details
Before you can calculate, you need to understand the information on the wallpaper label. The three most important figures are roll length, roll width, and pattern repeat.
Roll Length & Width: These define the total area of the roll. Standard UK/EU rolls are often 10m long and 52cm wide, while US rolls are typically 33ft long and 20.5in wide. Always check the specific product.
Pattern Repeat: This is the most critical factor for patterned wallpaper. It's the vertical distance on the wall before the pattern starts again. A large pattern repeat (e.g., 64cm) will result in more wastage than a small one (e.g., 10cm) because you have to cut the paper to ensure the pattern aligns perfectly from one strip to the next. For plain or "free match" wallpapers, you can enter '0' for this value.
Example Calculation
Let's see how it works with a real-world example:
Wall Dimensions: 2.5m high by 4m wide.
Wallpaper Roll: A standard 10m long, 52cm wide roll.
Pattern Repeat: A common 64cm repeat.
1. Drops Needed: The wall is 400cm wide and the paper is 52cm wide. 400 ÷ 52 = 7.69. You'll need to round up, so that's 8 drops (strips) to cover the wall.
2. Length of Each Drop: The wall is 250cm high. With a 64cm pattern repeat, you must cut the paper in multiples of 64cm that exceed the wall height. 4 x 64cm = 256cm. This is not enough once you add a trim allowance. 5 x 64cm = 320cm. This gives you enough length to match the pattern and trim the top and bottom. So, each drop will use 320cm of paper.
3. Drops Per Roll: The roll is 1000cm long. 1000cm ÷ 320cm = 3.125. You can only get 3 full drops from each roll.
4. Total Rolls: You need 8 drops, and you get 3 per roll. 8 ÷ 3 = 2.66. You must round up, so you need 3 rolls. Adding a 10% contingency for mistakes means you should buy 4 rolls to be safe.
Pro Tips for a Perfect Feature Wall
Batch Numbers: Always buy rolls from the same batch number, printed on the label. Colours can vary slightly between batches, which can be noticeable on the wall.
Wall Preparation: Ensure your wall is clean, dry, and smooth. Fill any cracks or holes and sand them down. Applying a wallpaper primer or "size" can help the paper adhere better and make it easier to remove later.
Always Add Contingency: Our calculator recommends a 10% contingency for a reason. Mistakes happen, especially when cutting around outlets or windows. It's always better to have a little extra than to run out.