Roof Shingle Calculator

Start from the flat footprint of the roof, add the pitch, and get sloped area, squares and bundles.

Worked example

Footprint 100 m² at 6/12 pitch. Slope factor = sqrt(1 + (6/12)²) = 1.118, so roof area = 100 x 1.118 = 111.8 m². With 10% waste: 123.0 m². Squares = 123.0 / 9.29 = 13.24 squares. Bundles = 13.24 x 3 = 39.7, rounded up to 40 bundles.

How it works

Roof area = footprint x slope factor, where the slope factor = sqrt(1 + (pitch / 12)²). One square covers 100 sq ft, which is 9.29 m². Standard architectural shingles take 3 bundles per square. Starter strips, ridge cap and underlayment are separate items and are not included in the bundle count.

FAQ

How do I get the footprint area?

Measure the building outline at ground level, including the eave overhang on all sides, and multiply length by width for each section. Dormers and attached garages are easiest handled as separate sections added together.

Do all shingles come 3 bundles to a square?

Most standard architectural shingles do. Some heavyweight or designer shingles need 4 or 5 bundles per square. Check the coverage printed on the bundle before ordering.

Estimates only. This calculator gives planning estimates, not professional advice. Measure the actual roof and verify quantities before ordering.