Roofing Calculator
Estimate roof area, shingle bundles, underlayment rolls, waste, and cost
Horizontal length of the roof footprint.
Horizontal width across the roof footprint.
Choose how you want to enter the roof slope.
Vertical rise for every 12 horizontal inches.
Roof slope angle measured from horizontal.
Extra for cuts, starter, caps, and mistakes.
Area covered by one shingle bundle or package.
Underlayment area covered by one roll.
Optional price per finished roof area.
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How This Roofing Calculator Works
Footprint area is adjusted for pitch, then waste and packaging are applied.
Start with the footprint
Enter horizontal length and width, not the sloped rafter length. The calculator treats that footprint as the flat area under the roof.
Apply the pitch factor
Pitch increases actual roof surface. A 6/12 roof has a factor of about 1.118, so 1,000 square feet of footprint becomes about 1,118 square feet of sloped roof.
Round purchase quantities
Bundles and underlayment rolls are rounded up to whole units after waste is added, so the purchase estimate does not under-cover the roof.
Roofing Calculator Examples
Typical roof measurement and material planning scenarios.
With 10% waste and 33.3 square feet per bundle, the estimate is about 1,181 square feet to buy.
Metric projects can use pitch degrees and square-meter bundle or panel coverage.
Enter roll coverage to see how many full underlayment rolls the roof area needs.
Roofing Calculator FAQ
Practical answers for roof pitch, shingles, waste, roofing squares, and purchase quantities.
Does the roofing calculator include roof pitch?
Yes. The calculator multiplies the horizontal footprint by a slope factor from either rise-over-run pitch or pitch degrees.
What waste allowance should I use for roofing?
Use about 10% for simple roofs. Increase it for hips, valleys, dormers, cut-up layouts, steep pitches, or if you want extra shingles for repairs.
What is a roofing square?
A roofing square is 100 square feet of roof area. It is commonly used for asphalt shingles in the United States.
Why are bundle counts rounded up?
Bundles, panels, and rolls are purchased as whole units, so the calculator rounds up to make sure the planned roof area is covered.
Can I use this for metal roofing or tile?
Use the roof area, waste area, perimeter, and price fields as planning values. Product-specific panel widths, overlaps, fasteners, and local roof details should be checked against the supplier instructions.