Roofing Calculator
Calculate roofing materials, shingles needed, and roofing costs. Free, fast, accurate — no signup, mobile-friendly, work
Roof Specifications
Common: 4/12, 6/12, 8/12
Base Roof Area
Before pitch adjustment
Roofing Requirements
Total Project Cost
$464/square
Roofing Squares
100 sq ft each
Net Roof Area
After pitch & openings
Cost Breakdown
Project Timeline
Roofing Tips
- • Schedule roofing work during dry, mild weather
- • Ensure proper ventilation to prevent ice dams
- • Check local building codes for material requirements
- • Consider energy-efficient materials for tax credits
- • Plan for proper disposal of old roofing materials
How it works
A roofing calculator estimates material from the roof area, measured in “squares” (one square = 100 square feet). Because roofs are pitched, the actual surface is larger than the building footprint, so a slope factor is applied.
Roofing squares
Roof area = footprint × slope factor Squares = roof area ÷ 100
- footprint
- ground area under the roof
- slope factor
- 1.05 (low) to 1.25+ (steep)
Worked example
- Footprint = 2,000 ft²
- Moderate pitch → slope factor 1.12
- Roof area = 2,000 × 1.12 = 2,240 ft²
- Squares = 2,240 ÷ 100
≈ 22.4 squares — order ~24 to cover waste and starter/ridge rows.
Good to know
- Steeper roofs have a bigger slope factor, so the same footprint needs more material.
- Add 10–15% for waste, plus extra for hips, valleys, and ridge caps.
- Three bundles of standard asphalt shingles typically cover one square.
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Frequently Asked Questions
How do I calculate how many shingles I need?
Find the roof area in squares (1 square = 100 sq ft), adjusting the footprint for pitch, then add 10-15% waste. Asphalt shingles are typically sold three bundles per square.
What is a roofing square?
One roofing square equals 100 square feet of roof surface. Contractors quote materials and labor per square, so a 2,000 sq ft roof is a 20-square job.
How does roof pitch affect the amount of material?
Pitch increases true surface area beyond the building footprint. Multiply the footprint by a pitch factor — about 1.05 for a shallow 3/12 roof, 1.12 for 6/12, and 1.41 for a steep 12/12.
How much waste factor should I add?
Add about 10% for a simple gable roof and 15% or more for roofs with hips, valleys, and dormers, which require more cutting. Starter strips and ridge caps also consume extra material.
What other materials does a roof need besides shingles?
Underlayment, drip edge, starter strips, ridge cap shingles, flashing for chimneys and valleys, and nails. Ice-and-water shield is required along eaves in cold climates by many building codes.