Roofing Squares & Bundles
Turn a roof footprint and pitch into squares, shingle bundles, starter, and ridge cap.
Estimates only — verify with local code and the product label.
How this works
This tool takes the roof's flat footprint — length and width, the way you'd measure it standing on the ground — and multiplies it by a pitch factor to get the actual sloped roof area, since a steeper roof has more surface than its footprint suggests. The pitch factor for an x/12 roof is sqrt(x² + 144) / 12; a 6/12 roof, for example, has about 11.8% more surface area than its footprint.
From there, squares (100 SF each, the standard roofing unit) get a waste allowance added before converting to bundles. Waste covers trim scrap, starter cuts, and mistakes, and it scales with how cut-up the roof is: 10% for a simple gable, up to 15% for something with several hips, valleys, and dormers. Architectural shingles are packaged 3 bundles to the square almost universally, so bundle count is just squares-with-waste times 3, rounded up to a whole bundle since suppliers don't sell partial ones.
Starter strip and ridge/hip cap are optional add-ons if you know your eave length and ridge/hip length — they're priced by linear feet of coverage per bundle (about 105 LF per starter bundle, about 25 LF per cap bundle), which are typical manufacturer numbers, not universal ones. Always check the wrapper on the actual product you're buying, since coverage varies by brand and profile.
This is a material takeoff, not a measurement service — it assumes you already know (or have measured) the footprint and pitch. For a satellite-based starting measurement of your own roof, see the Roof Estimate tool.
Frequently asked
Why 3 bundles per square?
It's how architectural/laminate shingles are packaged by virtually every major manufacturer, so 1 square (100 SF) of coverage comes from exactly 3 bundles. 3-tab shingles sometimes package differently — check your product.
How much waste should I use?
10% for a simple roof with few features, 12% for a moderate one with some hips or dormers, and 15% for a complex roof with lots of valleys and cuts. These are common contractor rules of thumb, not a fixed rule.
Does this replace a real measurement?
No — it turns a footprint and pitch you already know into squares and bundles. If you don't know your roof's measurements yet, start with the Roof Estimate tool.
Questions about a project? Contact us.