Choose the right dimensions.
Select horizontal plan dimensions if you measured the roof’s projection. Select roof surface dimensions if your lengths already follow the sloped plane.
Calculate roof square footage from horizontal dimensions and pitch, or use dimensions measured along the roof surface. Combine multiple sections and add a separate waste allowance.
Calculations run in your browser. This tool does not submit your measurements to a server.
Enter your roof dimensions.
One roofing square equals 100 square feet. Roofing squares are an area unit, not a bundle count.
| Section | Shape | Net area |
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Planning estimate only. Include overhangs in your dimensions, avoid overlapping sections, and verify measurements and material requirements before ordering. Product overlaps and pack rounding are not calculated here.
Select horizontal plan dimensions if you measured the roof’s projection. Select roof surface dimensions if your lengths already follow the sloped plane.
Break the roof into rectangles and triangles. Use a separate section for a different pitch. Divide a trapezoid into a rectangle and triangles.
Review the net surface area first. Then apply a suitable waste allowance. Material coverage, overlaps and package quantities need a separate check.
A rectangle uses length multiplied by perpendicular width. A triangle uses half its base multiplied by its perpendicular height. Triangle height is not the diagonal side.
Pitch adjustment applies only in horizontal-plan mode. In roof-surface mode, your dimensions already describe the sloped surface, so applying pitch again would overestimate the area.
For a roof with different slopes, calculate each section using its own pitch. Do not multiply the entire roof by a single pitch unless that pitch applies to every included plane.
Suppose a roof’s horizontal projected area is represented by a 40 ft by 30 ft rectangle, and all included roof planes have a 6:12 pitch.
The area including waste is a planning allowance, not a final shingle bundle or panel order.
Understand what to measure, when to apply pitch, and how to interpret your result.
No. Floor area can include multiple stories and does not directly describe the roof. Roof area depends on the horizontal roof projection, slope, overhangs and roof shape.
It depends on the section you are describing. For one plane of a symmetrical gable roof, use that plane’s horizontal projected width. If all planes have the same pitch, their combined non-overlapping horizontal projection can be calculated together. Do not then add those same planes again as separate sections.
No. Select “Roof surface — no pitch adjustment.” Use dimensions within the actual roof plane. The calculator disables pitch inputs to avoid applying slope twice.
Yes, when you can divide it into non-overlapping rectangular and triangular sections with known dimensions. Split trapezoids into a rectangle and triangles. Use each section’s actual pitch in horizontal-plan mode.
Enter the perpendicular distance from the selected base to the opposite vertex. Do not use a sloping triangle edge. In horizontal-plan mode, use the projected triangle’s perpendicular height, not the roof’s vertical rise.
Yes. Valid length inputs are converted when you switch units. Pitch and waste percentages remain unchanged. Calculate again to update the results.
No. There is no automatic opening deduction. Whether an opening should reduce an order quantity depends on cuts, layout and material requirements. Confirm your takeoff approach with your supplier or contractor.
No. It calculates surface area and roofing squares. Bundle quantities depend on the selected product’s stated coverage and the treatment of waste and accessories. Use the roof shingle calculator for that next step.