Roof Area Calculator
Find the true surface area of a sloped roof from the footprint and pitch — plus roof tiles or shingle bundles.
Assumes every roof plane has the same pitch. Dormers, valleys and different pitches need to be measured separately. Tiles per m² and bundles per square vary by product — check the manufacturer’s data sheet, and order ridge tiles, flashing and underlay separately.
About this tool
Enter the length and width of the roof measured over the eaves and the roof pitch in degrees or as rise per 12. The calculator applies the slope factor to give the real roof area in m² and ft², then estimates roof tiles (metric) or bundles of asphalt shingles (imperial) with a waste allowance.
Frequently asked questions
Measure the footprint over the eaves (including the overhang) and multiply it by the slope factor 1 ÷ cos(pitch). A 12 × 9 m footprint is 108 m²; at 30° the factor is 1.155, so the roof is 124.7 m².
Yes, as long as every roof plane has the same pitch. The area then depends only on the footprint and the pitch, so a hip roof and a gable roof over the same footprint have the same area. Measure dormers and planes with a different pitch separately.
It depends on the tile profile and batten spacing. Benders’ concrete tiles range from 8.9–10.8 per m² (Palema) to 11.4–12.9 per m² (Carisma), both for pitches from 14°. Use the figure from your tile’s data sheet.
A roofing square is 100 ft². Standard 3-tab and architectural asphalt shingles usually come 3 bundles per square, though some heavy designer shingles need 4–5. A 1,342 ft² roof is 13.4 squares — 45 bundles with 10% waste.
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