Roofing Calculator
Estimate roof area, shingle squares, bundles, and underlay rolls
Roof Length (ft)
ft
Roof Width (ft)
ft
Roof Pitch
Roof Sides
Waste / Overlap (%)
%
10% for simple roofs; 15–20% for complex cuts
Material Estimate
Footprint Area
—
Actual Roof Area
—
Area with Waste
—
Roofing Squares
—
Shingle Bundles
—
Felt Underlay
—
How Roofing is Measured
Roofing is sold in "squares" — 1 square covers 100 sq ft. Standard 3-tab asphalt shingles come 3 bundles per square (each bundle covers ~33 sq ft). The pitch factor accounts for the slope: a 6:12 pitch means the roof rises 6 inches for every 12 inches of horizontal run, making the actual surface 11.8% larger than the footprint.
Always add 10–15% waste for cuts, overlap, and damage. For complex roofs with valleys, hips, and dormers, use 15–20%. Enter the length and width of the roof footprint (the horizontal measurement, not the slope length).
lightbulb Example
40 × 30 ft gable roof, 6:12 pitch:
1Footprint: 40 × 30 = 1,200 sq ft
2Roof area: 1,200 × 1.118 × 2 = 2,683 sq ft
3With 10% waste: 2,951 sq ft = 30 squares
✓ 90 bundles of shingles needed