Roof Cost Calculator
Enter your measurements
Extra to cover cuts, breakage, and mistakes.
Results
- Roof area1,476 sq ft
- Roofing squares14.76 squares
- Footprint1,200 sq ft
- Slope multiplier1.118
Estimated cost
per roofing square, fully installed (asphalt)
Material cost per roofing square covers three-tab through mid-grade architectural shingles, underlayment, and basic fasteners. Installed price per square includes tear-off of one layer, synthetic underlayment, drip edge, standard flashing, and labor. Steep pitches above 8/12, two-story structures, complex roof geometry, and premium shingle lines all push costs toward or above the high end of these ranges.
Estimate only — prices vary by region, supplier, and season. Get a local quote before buying.
This roof cost calculator converts your home's footprint and roof pitch into the two numbers that drive every roofing bid: total roof area in square feet and roofing squares (the industry's unit of 100 sq ft). Enter your building's length, width, and pitch, and it applies the correct slope multiplier so you get the actual sloped surface area, not just the flat footprint, along with an installed price range for asphalt shingle work. Asphalt shingles are sold and priced by the square, so knowing your square count before you call a contractor prevents the most common estimating error: confusing floor area with roof area. A 6/12 pitch adds about 12 percent more surface than the footprint alone; an 8/12 adds roughly 20 percent, and a 12/12 adds over 40 percent. The calculator also applies a waste factor you can adjust: 10 percent is standard for a simple gable roof, while hips, dormers, and valleys typically need 15 percent or more.
How it’s calculated
Roof area = Footprint (Length × Width) × slope multiplier for the pitch. Squares = Roof area ÷ 100.
Worked example
For a house with a 45 ft by 32 ft footprint and a common 6/12 pitch, the calculator returns a slope multiplier of 1.118. That multiplier stretches the 1,440 sq ft footprint to 1,610 sq ft of actual roof surface, and the 10 percent waste factor brings the order quantity to 1,771 sq ft, or 17.71 roofing squares. That square count is exactly what a roofing contractor uses to price materials and labor, so walking into a quote with the number already in hand is a meaningful advantage.
Inputs
- Building length
- 45 ft
- Building width
- 32 ft
- Roof pitch (rise per 12)
- 6 /12
- Waste / overage
- 10 %
Result
- Roof area
- 1,771 sq ft
- Roofing squares
- 17.71 squares
- Footprint
- 1,440 sq ft
- Slope multiplier
- 1.118
- Estimated material cost
- $6,198 – $9,917
Materials & pricing near you
Asphalt shingles are sold by the square (100 sq ft of coverage). Three-tab products sit at the low end, while architectural (dimensional) laminate shingles dominate the mid-range and carry most manufacturers' best wind and warranty ratings; premium designer and impact-resistant (Class 4) grades sit at the top. Installed pricing swings with labor more than materials: Sun Belt and Midwest markets tend to run lower, while Northeast, California, and Pacific Northwest metros carry higher labor rates. A full tear-off and replacement almost always requires a permit; budget roughly $150 to $500 and confirm with your local building department before signing. Steep or two-story roofs also add staging and safety costs that a flat square count alone won't capture.
Frequently asked questions
What is a roofing square and why does it matter?
A roofing square equals 100 square feet of roof surface. Contractors price shingles, underlayment, and labor in squares, and standard architectural shingles are packaged so that three bundles cover one square. Knowing your square count lets you verify a contractor's material takeoff and compare bids on an apples-to-apples basis.
How do I measure my roof pitch if I don't know it?
Pitch is expressed as rise over a 12-inch run. From the attic, hold a level horizontally against a rafter, mark 12 inches along the level from where it meets the rafter, then measure straight down to the rafter; that vertical distance is your rise. Common residential pitches are 4/12, 6/12, and 8/12. A small smartphone pitch app held against a rafter or fascia gives a quick second opinion.
Should I use 10 percent or 15 percent for waste?
Use 10 percent for a straightforward gable roof with two clean planes and few penetrations. Increase to 15 percent for hip roofs, and 15 to 20 percent for roofs with multiple valleys, dormers, skylights, or irregular shapes, since each requires angled cuts that produce scrap. Running short mid-job costs more in delivery fees and delays than ordering a little extra upfront.
Does this calculator work for metal roofing or other materials?
The square footage and squares output applies to any roofing material, since the geometry is identical. However, the installed cost range shown is calibrated for asphalt shingles. Metal panels, tile, and wood shake carry very different material and labor costs, so use a material-specific calculator for those price estimates.