Roofing Calculator
Calculate the amount of roofing materials, costs, and dimensions you'll need for your roofing project quickly and accurately.
Enter Roofing Parameters
About Roofing Calculations
What is a Roofing Calculator?
A roofing calculator is a tool that helps homeowners, contractors, and builders estimate the amount of materials needed for roofing projects, as well as the associated costs.
It helps you plan your budget, order the right amount of materials, and avoid costly mistakes or excessive waste.
What is a Roofing Calculator?
A roofing calculator is a tool that helps homeowners, contractors, and builders estimate the amount of materials needed for roofing projects, as well as the associated costs.
It helps you plan your budget, order the right amount of materials, and avoid costly mistakes or excessive waste.
How to Use the Roofing Calculator
Follow these simple steps to get accurate estimates for your roofing project:
- Enter the base area of your house (the area covered by your roof when viewed from above)
- Select or enter your roof pitch (steepness)
- Input the width of your eave overhangs (how far the roof extends beyond your walls)
- Choose your roof shape and roofing material
- Click 'Calculate' to see detailed results including materials needed and cost estimates
For the most accurate results, try to measure your roof dimensions as precisely as possible, or refer to your house plans.
Roofing Calculation Formulas
Understanding the mathematics behind roofing calculations can help you verify results and make adjustments as needed:
Pitch Factor Calculation
The pitch factor accounts for the increased surface area due to the roof's slope. It's calculated as 1 divided by the cosine of the pitch angle in degrees. For example, a 6:12 pitch (approximately 26.57°) has a pitch factor of about 1.118, meaning the roof surface is 11.8% larger than the base area.
Roof Area Calculation
The total roof area is calculated by multiplying the base area by the pitch factor. This gives you the actual surface area of the roof that needs to be covered with roofing materials.
Eave Area Calculation
Additional area from eave overhangs is calculated based on the perimeter of the house and the width of the eave. For a rectangular house, this includes the perimeter multiplied by the eave width, plus the four corner areas (which are approximately the eave width squared).
Unit Conversions
- 1 squares = 100 sq ft
- 1 sq ft = 0.092903 sq m
- 1 sq ft = 0.111111 sq yd
Types of Roofs
Different roof styles have unique characteristics that affect material calculations:
Gable Roof
A simple roof with two sloping sides that meet at a ridge in the center, forming a triangle at each end. Gable roofs are one of the most common types and relatively straightforward for material estimation.
Hip Roof
A roof where all sides slope downward to the walls, usually with a fairly gentle slope. Hip roofs typically require more materials due to the additional hip ridges and more complex cutting patterns.
Mansard Roof
A four-sided roof with a double slope on all sides, with the lower slope steeper than the upper slope. Mansard roofs require more materials due to their complex shape and typically have a higher pitch factor.
Shed Roof
A single-sloped roof that typically slopes from one wall to another. Shed roofs are simple to calculate but may have different requirements for drainage and material types.
Butterfly Roof
A V-shaped roof formed by two tandem sections that slope inward toward the center. This inverse of a traditional roof requires special consideration for drainage and waterproofing at the center valley.
Flat Roof
A roof with a minimal slope, typically using different materials than pitched roofs. While called 'flat,' these roofs usually have a slight pitch for drainage and require special waterproofing considerations.
Roofing Materials
Different roofing materials have specific characteristics, weights, costs, and installation requirements:
Asphalt Shingles
The most common residential roofing material in North America, typically sold in bundles that cover about 33 square feet each. Three bundles usually make up one 'square' (100 sq ft) of roofing material.
Durability: 15-30 years depending on the quality and climate conditions.
Metal Roofing
Available in panels or shingles, metal roofing is durable, lightweight, and fire-resistant. It's typically sold in panels of various sizes or in squares for metal shingles.
Durability: 40-70 years for quality installations.
Concrete or Clay Tile
Tiles provide a distinctive appearance and excellent durability but are heavy and may require additional structural support. They're typically sold by piece, with each tile covering a specific area.
Durability: 50+ years for clay tiles, 30-50 years for concrete tiles.
Slate
Natural stone slate tiles are among the most durable roofing materials available but are also among the heaviest and most expensive. Each slate typically covers about 1 square foot.
Durability: 75-200 years, making it one of the longest-lasting roofing materials.
Wood Shingles/Shakes
Made from cedar, redwood, or other rot-resistant woods, these provide a natural look but require more maintenance. They're typically sold in bundles covering 25-33 square feet.
Durability: 25-30 years with proper maintenance.
Frequently Asked Questions
How accurate are the material estimates from this calculator?
Our calculator provides estimates that are typically within 10-15% of the actual materials needed for most standard roof configurations. For very complex roofs with multiple intersections, dormers, or unusual shapes, we recommend adding an additional 5-10% to the estimates or consulting with a professional roofer.
Why does the calculator ask for eave width?
Eaves (the part of the roof that extends beyond the walls) add significant area to the total roofing requirement. Including the eave width provides a more accurate material estimate, especially for houses with substantial overhangs.
How do I determine my roof pitch?
The easiest way is to use a level and tape measure on the rafters in your attic. Place the level horizontally, measure 12 inches along it, then measure vertically from that point to the rafter. The vertical measurement in inches gives you the rise in a 12-inch run (e.g., 6 inches rise = 6:12 pitch). Alternatively, you can use a smartphone with a pitch-measuring app.
What waste factor should I choose?
For simple gable or shed roofs, 10-15% is typically sufficient. For hip roofs or roofs with valleys, choose 15-20%. For very complex roofs with multiple intersections, dormers, or unusual shapes, use 20-25% or higher.
Do I need to include existing roofing in my calculations if I'm replacing a roof?
This calculator estimates materials for the roof surface area. If you're replacing an existing roof, you should also consider potential additional costs for tear-off, disposal, and any necessary repairs to the roof deck, which aren't included in these calculations.