Roofing Calculator
Shingle bundles, roofing squares, roof pitch, roof area and gutter sizing - all the math you need to order materials before the job.
How many bundles of shingles do I need? What is a roofing square? What is the angle of a 6/12 pitch? How do I convert building footprint to actual roof area? These roofing calculators cover the whole materials takeoff: shingle bundles and starter strips, roof pitch and angle, roof area from footprint, underlayment and ice and water shield, and gutter and downspout sizing by drainage area. Every tool includes the industry-standard waste factor - 10% for simple gable roofs, 15% for hips with valleys and 20% for complex roofs with dormers and skylights.
Frequently asked questions
Most asphalt shingles come 3 bundles per square (100 sq ft of roof). A 2,000 sq ft roof with 10% waste = 22 squares = 66 bundles. Premium designer shingles come 4 bundles per square. Always add starter strip bundles (1 per ~100 ft of eaves) and ridge cap bundles (1 per ~20 ft of ridge).
Multiply the footprint by the pitch factor: sqrt((rise/12)^2 + 1). A 6/12 pitch multiplier is 1.118. A 40x30 ft footprint with a 6/12 gable roof = 1,342 sq ft of roof surface. Add eave overhang to the footprint dimensions before multiplying.
A 6/12 pitch equals 26.57 degrees. Other common pitches: 4/12 = 18.43 degrees, 8/12 = 33.69 degrees, 12/12 = 45 degrees. Use the roof pitch calculator to convert between rise/run, degrees and the area multiplier.
For a 5-inch K-style gutter in average US rainfall, one downspout per 600 sq ft of roof drainage area. A 2,000 sq ft roof = 4 downspouts minimum. Bump up in heavy-rain regions (Gulf Coast, parts of FL) or use 6-inch gutters that handle 2x the volume per downspout.
Synthetic for almost every job. It is 5x lighter, lays flat without curling and rolls cover 1000 sq ft vs 200-400 for felt. Felt is now mostly used for budget jobs or warranty compliance. Ice and water shield is still required by code along eaves in cold climates regardless of underlayment choice.
All roofing tools
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