Roofing Calculator
Estimate roofing materials needed based on your roof dimensions and pitch.
About the Roofing Calculator
Replacing or installing a roof is one of the largest home improvement investments. Knowing how many shingles, squares, and underlayment rolls you need before calling contractors helps you budget accurately and verify quotes are reasonable.
What Is a Roofing Square?
A roofing square equals 100 square feet of roof surface. This is the standard unit used by roofing contractors and materials suppliers. A typical 2,000 sq ft home might have 20–25 squares when accounting for pitch and overhang.
Understanding Roof Pitch
Pitch is expressed as "rise over run" — how many inches the roof rises for every 12 inches of horizontal run. A 4/12 pitch is common for residential homes (moderate slope). Higher pitches increase the actual surface area because the roof is steeper. The pitch multiplier for area calculation: √((rise² + 144) / 144).
Waste Factor
Always add a waste factor for cuts, hips, valleys, and edges: Simple gable roof: +10% | Complex roof with multiple valleys/hips: +15–20% | Very complex or steep roof: +20–25%.
Shingles per Square
Standard 3-tab shingles: 3 bundles per square (about 26 shingles/bundle). Architectural shingles: typically 3–4 bundles per square. Always verify with the specific product you purchase.
Other Materials to Estimate
Underlayment: 1 roll per 4 squares (varies by product). Ridge cap shingles: Count linear feet of ridge and hip, divide by 35 for bundles. Drip edge: Measure perimeter in linear feet. Roofing nails: Approximately 2 lbs per square.
When to Replace vs. Repair
Asphalt shingles last 20–30 years. If more than 30% of shingles are damaged, replacement is usually more cost-effective than repair. A full replacement also allows inspection and replacement of underlayment and decking.