Choosing the right amount of roofing shingles and estimating their cost is crucial for any roofing project. This calculator helps you determine the number of shingles and bundles required for your roof, along with an estimated cost, by considering the dimensions of your roof and common industry factors.
How the Calculator Works:
The calculation is based on a few key inputs:
Roof Length and Width: These measurements are used to calculate the total surface area of your roof in square feet. The formula is Area = Length × Width.
Shingles per Square: Roofing materials are often sold and measured in "squares," where one square covers 100 square feet. This input defines how many bundles of shingles are typically needed to cover one such square. A common number is 3 bundles, but this can vary by shingle type and manufacturer specifications.
Waste Factor: Roofing involves cutting and fitting, which inevitably leads to some material waste. A waste factor (usually 5-15%) is added to account for this. This ensures you order enough material to complete the job without running short.
Cost per Bundle: This is the price you pay for a single bundle of shingles. Entering this value allows the calculator to provide a total estimated cost.
The Calculation Process:
Calculate Total Roof Area:
Total Area (sq ft) = Roof Length (ft) × Roof Width (ft)
Calculate Number of Squares:
Number of Squares = Total Area (sq ft) / 100 sq ft/square
Calculate Total Shingles Needed (including waste):
Gross Shingles = Number of Squares × Shingles per Square
Total Shingles Required = Gross Shingles + Waste Amount
Calculate Number of Bundles: Since shingles are usually sold in bundles, and the "shingles per square" often implies a bundle count for that square:
Total Bundles = Total Shingles Required / Shingles per Square
We round this up to the nearest whole number because you cannot buy partial bundles.
Calculate Total Cost:
Estimated Cost = Total Bundles × Cost per Bundle
Disclaimer: This calculator provides an estimate based on the inputs provided. Actual material needs can vary due to roof complexity (e.g., valleys, hips, dormers), specific shingle patterns, and local building codes. Always consult with a professional roofing contractor for an accurate quote and assessment.
function calculateShingles() {
var roofLength = parseFloat(document.getElementById("roofLength").value);
var roofWidth = parseFloat(document.getElementById("roofWidth").value);
var shinglesPerSquare = parseFloat(document.getElementById("shinglesPerSquare").value);
var wasteFactor = parseFloat(document.getElementById("wasteFactor").value);
var costPerBundle = parseFloat(document.getElementById("costPerBundle").value);
var resultDiv = document.getElementById("result");
resultDiv.innerHTML = 'Results will appear here.'; // Clear previous results
if (isNaN(roofLength) || isNaN(roofWidth) || isNaN(shinglesPerSquare) || isNaN(wasteFactor) || isNaN(costPerBundle)) {
resultDiv.innerHTML = "Please enter valid numbers for all fields.";
return;
}
if (roofLength <= 0 || roofWidth <= 0 || shinglesPerSquare <= 0 || wasteFactor < 0 || costPerBundle < 0) {
resultDiv.innerHTML = "Please enter positive values for dimensions and shingles per square, and non-negative values for waste factor and cost.";
return;
}
var totalArea = roofLength * roofWidth;
var numberOfSquares = totalArea / 100;
var grossShingles = numberOfSquares * shinglesPerSquare;
var wasteAmount = grossShingles * (wasteFactor / 100);
var totalShinglesRequired = grossShingles + wasteAmount;
var totalBundles = Math.ceil(totalShinglesRequired / shinglesPerSquare); // Assuming shinglesPerSquare directly correlates to bundles per square
var estimatedCost = totalBundles * costPerBundle;
resultDiv.innerHTML =
"Total Roof Area: " + totalArea.toFixed(2) + " sq ft" +
"Estimated Number of Squares: " + numberOfSquares.toFixed(2) + "" +
"Estimated Bundles Needed (with waste): " + totalBundles + "" +
"Estimated Total Cost: $" + estimatedCost.toFixed(2) + "";
}