Roofing Calculator
Calculate the number of roofing squares and shingle bundles needed for a roof area, including waste.
- Base Roof Area18 squares · 91%
- Waste Allowance1.8 squares · 9%
Your 10% waste factor adds 1.8 extra squares on top of the roof's actual area, to cover cuts, overlaps and hips/valleys.
- Shingle Bundles (≈3/square)60
About the Roofing Calculator
This calculator converts a roof's area into roofing squares — the unit roofers actually price and order material in — along with an estimated shingle bundle count, so you have real numbers before a materials run or a contractor quote.
It's used ahead of a reroofing project to estimate material cost, to sanity-check a contractor's quoted square count against the roof's actual measured area, or to plan a DIY shed or garage roof from scratch.
Roof area is trickier to measure than floor area since it includes slope, hips, valleys and ridge lines that a simple footprint measurement misses — this calculator assumes you're entering the actual roof surface area (not the building's footprint), with a waste factor built in to cover the cuts and overlaps that measurement alone won't catch.
How it’s calculated
A roofing square is a standard unit equal to 100 square feet of roof surface — dividing total roof area by 100 gives the base square count. Adding a waste percentage on top accounts for material lost to angled cuts around hips, valleys and ridges, plus normal shingle overlap, both of which increase actual material needed beyond the roof's raw area.
Shingle bundles are estimated at roughly 3 bundles per square, which is standard for most architectural and 3-tab asphalt shingles, though some heavier or specialty shingle products may require a different bundle-per-square ratio — check the product packaging for the exact coverage rate.
Frequently asked questions
What's a typical waste factor for a roofing project?
10% is a common default for a straightforward gable roof; more complex rooflines with lots of hips, valleys, dormers or a steep pitch often warrant 15% or more to cover the extra angled cuts those features require.
How many shingle bundles come in a square?
Most standard asphalt shingles are packaged 3 bundles to a square (100 sq ft), which is the ratio this calculator uses — but always confirm against the specific product's packaging, since some heavier or specialty shingles use a different bundle count per square.
How do I measure roof area if I can't get on the roof?
Satellite measurement tools, a contractor's roof measurement report, or measuring the building's footprint and multiplying by a pitch-based multiplier are all common approaches — a steeper roof has meaningfully more actual surface area than its footprint alone suggests.
Should I order extra beyond the calculated bundle count?
Rounding up to the next full bundle (which the calculator already does) plus keeping the waste factor generous for a complex roof is usually enough — running short mid-project, especially on a specific shingle color batch, is more costly than having a spare bundle or two on hand.
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