Simple (Gable Roof)
Moderate (Hips and Valleys)
Complex (Multiple Dormers/Levels)
Estimated Replacement Cost
*Disclaimer: This is an automated estimate. Actual quotes may vary based on local labor rates, tear-off requirements, and structural repairs.
How to Estimate Your Roofing Costs
Estimating the cost of a new roof involves more than just measuring the ground floor of your home. To get an accurate figure, contractors look at the "Roofing Square." One roofing square equals 100 square feet of roof surface area.
Key Factors Influencing Your Estimate:
Roof Pitch: Steeper roofs have more surface area than flat ones for the same footprint. They also require more safety equipment and labor time, increasing the cost.
Material Choice: Asphalt shingles are the most budget-friendly, while materials like slate or copper can cost five times as much but last significantly longer.
Waste Factor: Every roof requires cutting materials to fit valleys and hips. A standard 10% to 15% waste factor is usually added to the total square footage.
Complexity: A simple "Up and Over" gable roof is much cheaper to install than a roof with multiple dormers, chimneys, and intersecting roof lines.
Example Calculation
If you have a 2,000 sq. ft. home with a standard pitch (1.15 multiplier) and moderate complexity (1.15 multiplier), your actual roof surface area is roughly 2,300 sq. ft. Adding a 10% waste factor brings you to 2,530 sq. ft. (or 25.3 squares). If you choose architectural shingles at $8.50 per sq. ft. (installed), your estimated cost would be approximately $21,505.
When should you replace your roof?
Most asphalt roofs last 20-25 years. Look for curling shingles, granules in the gutters, or water spots on your ceiling. If more than 30% of your roof is damaged, a full replacement is usually more cost-effective than multiple repairs.
function calculateRoofCost() {
var footprint = parseFloat(document.getElementById('houseSqFt').value);
var pitchMultiplier = parseFloat(document.getElementById('roofPitch').value);
var materialPrice = parseFloat(document.getElementById('materialType').value);
var complexityMultiplier = parseFloat(document.getElementById('complexity').value);
var resultBox = document.getElementById('roofResultBox');
var totalDisplay = document.getElementById('totalEstimate');
var detailsDisplay = document.getElementById('breakdownDetails');
if (isNaN(footprint) || footprint <= 0) {
alert("Please enter a valid square footage.");
return;
}
// 1. Calculate Surface Area based on pitch
var surfaceArea = footprint * pitchMultiplier;
// 2. Add standard 10% waste factor
var totalAreaWithWaste = surfaceArea * 1.10;
// 3. Calculate Base Cost (Area * Material Price)
var baseCost = totalAreaWithWaste * materialPrice;
// 4. Apply Complexity Multiplier (Labor increase)
var finalEstimate = baseCost * complexityMultiplier;
// 5. Calculate Roofing Squares (1 square = 100 sq ft)
var squares = totalAreaWithWaste / 100;
// Formatting numbers
var formattedTotal = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
}).format(finalEstimate);
// Display Results
totalDisplay.innerText = formattedTotal;
detailsDisplay.innerHTML = "Breakdown:" +
"- Estimated Roof Surface: " + Math.round(totalAreaWithWaste) + " sq. ft. (incl. waste)" +
"- Total Roofing Squares: " + squares.toFixed(2) + " squares" +
"- Estimated Material & Labor: " + (materialPrice * complexityMultiplier).toFixed(2) + " per sq. ft.";
resultBox.style.display = 'block';
// Smooth scroll to result
resultBox.scrollIntoView({ behavior: 'smooth', block: 'nearest' });
}