Roof Square Footage Calculator
Enter your roof's footprint and pitch to get the real surface area, roofing squares, and shingle bundles -- not just the flat footprint.
Roofing squares to order
14.8 squares
(1476 sq ft of roof surface, waste included)
Footprint
1200 sq ft
Pitch multiplier
1.118
Shingle bundles
45
Material cost
--
At the defaults above (a 40x30 ft footprint, 6/12 pitch, 10% waste) that's about 14.8 squares and 45 bundles.
How it's calculated
The footprint (length × width, or a total you already worked out on the square footage calculator) is multiplied by the pitch factor to get the sloped surface area, then a waste allowance is added before converting to roofing squares. A roofing square is 100 sq ft -- the unit shingles, underlayment, and labor are priced in -- and three bundles of standard shingles cover one square. The pitch multiplier is computed directly from the X/12 rise-and-run ratio rather than read off a rounded lookup table, so any pitch works, not just the common ones.
Keep going
- Need the building's footprint first? Measure it here, including odd shapes and cutouts, then bring that number into the roof calculator. Square Footage Calculator
- Re-roofing often comes with exterior touch-ups; the paint calculator sizes primer and paint for the walls or trim. Paint Calculator
Frequently Asked Questions
What is a roofing "square"?
A fixed industry unit equal to 100 sq ft of roof surface -- shingles, underlayment, and labor are all priced and ordered by the square rather than the raw square footage, which is why this calculator converts to squares as the main result.
How does pitch affect the square footage?
A sloped roof's actual surface is larger than the building's flat footprint. For an X/12 pitch (X inches of rise per 12 inches of run), the roof plane is the hypotenuse of a right triangle with legs 12 and X, so the multiplier is exactly sqrt(12² + X²) / 12 -- this calculator computes that directly rather than reading it off a rounded table.
Does this work for a hip roof, not just a gable?
The footprint-times-pitch-multiplier method is the standard estimating shortcut for both, and it's what this calculator uses. A hip roof's hips and valleys add real cutting complexity a professional measurement accounts for more precisely, so treat this as a solid planning estimate, not a substitute for an actual roof measurement before ordering material for a complex roof.
Why does the calculator add waste on top of the raw area?
The 10% default covers cut waste, starter courses, ridge cap, and the extra material hips and valleys use -- a standard allowance in roofing estimates, the same convention this site's other material calculators use.
How many bundles of shingles is that?
Three bundles of standard shingles cover one square (300 sq ft total per bundle across the three), a convention old enough to predate any particular shingle brand. This calculator uses that ratio for the bundle count.
Can I find my roof's square footage from an address instead of measuring it?
Not with this tool -- it works from a footprint you enter (length × width, or the total from the square footage calculator) plus pitch. Satellite-measurement tools exist for an address-based estimate, but they're a different kind of tool than a measurement calculator.