Roofing Calculator
Accurately estimate your roofing materials and costs. Calculate the total roof area, shingles, underlayment, and ridge caps needed for your project.
Roof Diagram
This calculator assumes a simple gable or hip roof. For complex roofs with multiple sections, calculate each as a separate rectangle.
The Complete Guide to Estimating Roofing Materials
A roofing project, whether a small repair or a full replacement, requires careful planning. The most important step is accurately estimating the amount of materials needed. This prevents costly over-ordering and frustrating mid-project material shortages. Our roofing calculator uses the same method professionals use—footprint and pitch—to give you a reliable estimate.
Key Roofing Terms Explained
- Footprint: The area of the building covered by the roof, as measured at ground level (Length × Width).
- Roof Pitch: The steepness or slope of your roof. It's expressed as a ratio of "Rise" over "Run". For example, a "4/12" pitch means the roof rises 4 inches for every 12 inches of horizontal distance.
- Roofing Square: The standard unit of measurement in the roofing industry. One square is equal to 100 square feet. Shingles and other materials are typically sold and priced "by the square".
- Waste Factor: It's impossible to use every single piece of shingle due to cuts needed for hips, valleys, and edges. A waste factor of 10-15% is standard to account for this. Complex roofs with many angles require a higher waste factor.
How to Measure Your Roof
- Measure the Footprint: Using a tape measure, find the length and width of your house at the exterior walls.
- Determine the Pitch: Safely place a level horizontally against a rafter in your attic. Measure 12 inches from the end of the level, and then measure the vertical distance from that point up to the bottom of the rafter. That vertical measurement is your "Rise".
- Measure the Eaves: Measure the distance your roof hangs over the wall. This is your eave overhang.
- Enter into the Calculator: Input these values into the calculator above to get your total roof area and material needs.
Related Construction & Project Planning Tools
A new roof is often part of a larger project. To calculate the exterior wall area for siding, you can use our Square Footage Calculator. If you're building from the ground up, our Stair Calculator and Concrete Calculator will be essential. Considering the project's impact on your finances? Explore options with our Loan & Mortgage Calculator.