Flat / Low Slope (Walkable)
Medium Slope (Standard Gable)
Steep Slope (Difficult to walk)
Very Steep (Requires safety harness)
Asphalt Shingles (3-Tab) – Economy
Architectural Shingles – Standard
Metal Roofing (Steel)
Clay/Concrete Tile
Natural Slate
Includes estimated material and labor cost per sq ft.
No (Overlay existing)
Yes (1 Layer)
Yes (2 Layers/Complex)
Base Material & Labor:$0.00
Pitch/Difficulty Surcharge:$0.00
Tear-off Cost:$0.00
Waste Factor (10%):$0.00
Estimated Total:$0.00
*Estimates are national averages. Local labor rates and supply availability will vary.
function calculateRoofCost() {
// 1. Get Input Values using explicit getElementById
var areaInput = document.getElementById('roofArea').value;
var pitchMultiplier = parseFloat(document.getElementById('roofPitch').value);
var materialCostPerSqFt = parseFloat(document.getElementById('roofMaterial').value);
var tearOffCostPerSqFt = parseFloat(document.getElementById('tearOff').value);
// 2. Validate Input
var area = parseFloat(areaInput);
if (isNaN(area) || area <= 0) {
alert("Please enter a valid roof area in square feet.");
return;
}
// 3. Calculation Logic
// Base cost is area * material rate
var baseCost = area * materialCostPerSqFt;
// Pitch surcharge calculation: The multiplier applies to the labor/difficulty aspect.
// For simplicity in this estimation, we apply the multiplier to the base cost to represent increased surface area and labor difficulty.
// However, technically pitch increases actual square footage.
// Logic: Adjusted Area = Area * PitchMultiplier? No, PitchMultiplier is usually cost factor.
// Let's treat the Pitch Multiplier as a complexity factor on the Base Cost.
// Base Cost (Flat) vs Base Cost (Steep).
var totalBaseAndPitch = baseCost * pitchMultiplier;
var pitchSurcharge = totalBaseAndPitch – baseCost;
// Tear off calculation
var tearOffTotal = area * tearOffCostPerSqFt;
// Waste Calculation (standard 10% for cuts and overlaps)
var subTotal = totalBaseAndPitch + tearOffTotal;
var wasteCost = subTotal * 0.10;
// Final Total
var grandTotal = subTotal + wasteCost;
// 4. Formatting Output (USD)
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
});
// 5. Update the DOM
document.getElementById('res-base').innerHTML = formatter.format(baseCost);
document.getElementById('res-pitch').innerHTML = formatter.format(pitchSurcharge);
document.getElementById('res-tearoff').innerHTML = formatter.format(tearOffTotal);
document.getElementById('res-waste').innerHTML = formatter.format(wasteCost);
document.getElementById('res-total').innerHTML = formatter.format(grandTotal);
// Show result div
document.getElementById('roofing-result').style.display = 'block';
}
Understanding Roofing Replacement Costs
Calculating the cost of a new roof is one of the most significant budgeting tasks for a homeowner. While the national average for a roof replacement ranges between $5,500 and $11,000, the final price tag depends heavily on the materials chosen, the size of your home, and the structural complexity of your existing roof.
Key Factors Affecting Your Roof Estimate
Our Roofing Cost Calculator takes into account the four primary variables that contractors use to generate a quote:
Square Footage (The "Square"): Roofers measure surfaces in "squares," where one square equals 100 square feet. Accurate measurement of the footprint plus the overhangs is crucial.
Roof Pitch (Steepness): A steeper roof is more dangerous to work on and requires more safety equipment, staging, and time. Low-slope roofs are generally cheaper to install but may require specific membranes to prevent leaks.
Material Choice: Asphalt shingles are the most common and cost-effective option. Metal roofing offers longevity but comes at a higher upfront cost (often 2-3x asphalt). Premium materials like slate or clay tile are the most expensive but can last over 50 years.
Tear-Off vs. Overlay: Removing the old shingles (tear-off) adds labor and disposal fees ($1,000 to $3,000 typically). While layering new shingles over old ones saves money, it can mask underlying structural issues and shorten the lifespan of the new roof.
Why Is Waste Factor Important?
You will notice a "Waste Factor" included in your calculation. When installing a roof, materials must be cut to fit valleys, hips, and ridges. Professional contractors typically order 10% to 15% extra material to account for these cuts and potential breakage during shipping. Ignoring this buffer can lead to material shortages mid-project.
Common Roofing Material Prices (2024 Estimates)
To help you budget, here is a breakdown of average installed costs per square foot:
3-Tab Asphalt Shingles: $3.50 – $5.50 per sq. ft.
Architectural Shingles: $5.00 – $8.00 per sq. ft.
Metal Roofing: $9.00 – $14.00 per sq. ft.
Slate or Tile: $15.00 – $30.00+ per sq. ft.
When Should You Replace Your Roof?
It is recommended to inspect your roof twice a year. Signs that you need a replacement rather than a repair include widespread curling shingles, missing granules (bald spots), daylight visible through roof boards in the attic, or a roof age exceeding 20 years (for asphalt shingles). Using this calculator can help you prepare financially before the leaks begin.