Roofing Shingle Calculator
Estimate roofing squares and the number of shingle bundles to buy, from your roof area or a footprint and pitch, plus a waste cushion.
How it works
Roofers measure in squares, and one square is 100 square feet of roof surface. If you've already measured the actual sloped area, punch it in. If you only know the building's footprint, pick a pitch and the calculator multiplies the footprint by a slope factor to estimate the real surface area you have to cover.
From there it adds your waste percentage, divides by 100 to get squares, and multiplies by three, since architectural shingles come three bundles to the square. Bundles round up because you can't buy a fraction of one — better a few leftover than a bald patch near the ridge.
Ten percent waste is a sensible default for a straightforward gable roof; bump it toward fifteen for lots of hips, valleys, and cut-up sections where more shingles end up as off-cuts. The result is the bundle count to bring home before you factor in starter strip and ridge caps.
Frequently asked questions
Why does 100 square feet equal one square and three bundles?
A roofing square is defined as 100 square feet, and standard architectural shingles are packaged three bundles per square. So 100 square feet is exactly one square, which is three bundles — before any waste is added.
I only know my house footprint. Can I still estimate?
Yes. Switch to a pitch option and enter the ground footprint. The tool multiplies by a slope factor — steeper roofs have more surface per square foot of footprint — to approximate the actual roof area, then works out squares and bundles from that.
How much waste should I plan for?
Around 10 percent covers a simple roof with few cuts. Complex roofs with several valleys, dormers, and hips waste more, so 15 percent is safer there. This only counts field shingles — buy starter and ridge cap separately.