Roofing Calculator

Building footprint and pitch — roof area, squares, and shingle bundles.

ft
ft
/12
%
Roof area
1,342 sq ft
Squares (with waste)
14.76
Bundles of shingles
45

A "square" is roofing shorthand for 100 sq ft of coverage — standard three-tab shingles cover about a third of a square per bundle, so 3 bundles per square.

A worked example

A 1,200 sq ft footprint with a 6/12 pitch has a roof area of about 1,342 sq ft — roughly 15% more than the flat footprint, due to the slope.

Frequently asked questions

Why is roof area bigger than the building's footprint?

A pitched roof is tilted, so its actual surface area is always larger than the flat footprint below it — the steeper the pitch, the bigger that difference becomes.

What does a pitch of '6/12' mean?

It means the roof rises 6 inches vertically for every 12 inches of horizontal run — a fairly moderate, common residential pitch. A '12/12' pitch is a steep 45-degree roof.

Why 3 bundles per square?

It's the standard coverage for traditional three-tab asphalt shingles — three bundles together cover almost exactly 100 square feet (one "square") with the right amount of overlap.