Roofing Calculator
Use this free roofing calculator to estimate roof surface area, roofing squares, shingle bundles, waste and material cost. Enter the building dimensions and roof pitch to get a quick material estimate.
Roofing Calculator
Smart EstimateRoof area, shingles, bundles and material cost
Building dimensions
ftRise per 12 units of run.
Extra material for cuts.
Use the coverage shown on your shingle package. One U.S. roofing square equals 100 ft² (9.290304 m²).
$Optional material cost▼
Material estimate only. No live currency conversion is used.
Note: Hips, valleys, dormers, overhangs and roof complexity can change material needs. Verify the final quantity with your supplier or roofing contractor.
ROOFING CALCULATION
How to Calculate Roofing
Roofing quantity depends on the building footprint, roof pitch, material coverage and waste. A pitched roof has more surface area than its flat footprint because the roof slopes upward. For a building footprint calculation, use our Area Calculator.
1. Footprint
Length × Width
Calculate the flat building footprint.
2. Roof Area
Footprint × Pitch Factor
Adjust the footprint for the roof slope.
3. Material
Area + Waste
Convert the adjusted area into roofing squares and bundles.
Roofing Calculator Formula
Building Footprint: Length × Width
Pitch Multiplier: √(1 + (Rise ÷ 12)²)
Roof Surface Area: Footprint × Pitch Multiplier
Order Area: Roof Area × (1 + Waste ÷ 100)
Roofing Squares (Imperial): Order Area ÷ 100 ft²
Roofing Squares (Metric): Order Area ÷ 9.290304 m²
Shingle Bundles: Order Area ÷ Bundle Coverage
Bundle quantities are rounded up to the next whole bundle. One U.S. roofing square is 100 ft², equivalent to 9.290304 m².
Roofing Calculator Example
Suppose a building is 40 ft long and 30 ft wide with a 6:12 roof pitch and 10% waste. This example assumes a simple roof shape and does not separately add overhangs.
Common Roofing Calculator Uses
Homeowners and contractors can use a roof estimate to plan shingle purchases, compare material quantities and prepare an initial budget. For related construction estimates, see our Paint Calculator and Gravel Calculator.
Roofing Calculator FAQ
What is a roofing square?
One U.S. roofing square equals 100 square feet (9.290304 square meters) of roof surface area. Roofing contractors commonly use roofing squares when estimating shingles and other roofing materials.
How do I calculate roof area from pitch?
Multiply the building length by its width to find the footprint. Then multiply the footprint by the pitch multiplier: √(1 + (rise ÷ 12)²). This estimates the sloped roof area for a simple roof shape.
How many shingle bundles are in a roofing square?
Some common asphalt shingles require about three bundles per roofing square, but coverage varies by product. Check the coverage printed on the package for a more reliable estimate.
How much roofing waste should I add?
A simple roof may need around 5% to 10% extra material. Roofs with hips, valleys, dormers, penetrations and many cuts may need more. The correct allowance depends on roof design and material.
Can I use this roofing calculator in metric units?
Yes. Select Metric to enter dimensions in meters and bundle coverage in square meters. One U.S. roofing square equals 9.290304 square meters.
Does the roofing cost estimate include labor?
No. The optional cost estimate uses the material price per roofing square you enter. Labor, roof removal, underlayment, flashing, delivery and other accessories are excluded.
Can I use this calculator for a complex roof?
It provides a planning estimate for a simple roof shape. Complex roofs should be divided into individual roof planes or measured with a detailed roof takeoff. Overhangs, valleys, hips, dormers and penetrations can change material quantities.
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Important Note
This calculator provides a material-planning estimate. Actual roofing quantities depend on roof geometry, overhangs, valleys, hips, dormers, penetrations, product coverage and installation waste. Confirm the final quantity with your roofing supplier or a qualified roofing professional.
Roofing Resources and Further Reading
Explore these resources for general information about roofing materials, roof performance and energy efficiency.
- U.S. Department of Energy: Cool Roofs — Learn how reflective roofing can affect heat absorption and building energy use.
- U.S. Department of Energy: Cool Asphalt Shingles — Explore information on asphalt shingle reflectance and roofing performance.
- Better Buildings: Roofing Resources — Read about roofing systems and building energy efficiency.
These resources provide general educational information. Always follow the selected roofing product manufacturer's installation instructions and local building requirements.