Roofing Calculator
Free online roofing calculator to estimate roof area and materials needed. Calculate by roof pitch or angle, including eaves overhang. Get estimates for shingles, felt, and roofing materials.
Roofing Area Calculator (Roof Pitch or Roof Angle)
Roofing Material Calculator
What is a Roofing Calculator?
A Roofing Calculator is an essential tool for contractors, builders, and homeowners to estimate the area of a roof and calculate the materials needed for roofing projects. It accounts for roof pitch (slope), roof angle, and eaves overhang to provide accurate measurements. This helps in ordering the right amount of shingles, felt, and other roofing materials, reducing waste and ensuring you have sufficient supplies.
Understanding Roof Pitch
Roof pitch is expressed as a ratio of vertical rise to horizontal run, measured in inches. For example, a 6/12 pitch means the roof rises 6 inches for every 12 inches of horizontal run. Pitch directly affects the roof area - steeper roofs have more surface area than flat roofs with the same base.
- Low Pitch (1/12 to 4/12): Nearly flat roofs, common in commercial buildings and modern homes. Angle: 4.8° to 18.4°
- Medium Pitch (5/12 to 9/12): Standard residential roof pitch, good balance of aesthetics and functionality. Angle: 22.6° to 36.9°
- High Pitch (10/12 to 12/12): Steep roofs, excellent water drainage and snow shedding. Angle: 39.8° to 45°
- Very Steep (13/12+): Dramatic architectural style, requires special safety measures. Angle: 47.3°+
Roofing Formulas
Convert Pitch to Angle:
Angle = arctan(Pitch / 12)
Calculate Roof Area from Base:
Roof Area = Base Area × Pitch Multiplier
Pitch Multiplier = √(1 + (Pitch/12)²)
Including Eaves Overhang:
Total Area = Roof Area + Eaves Area
Common Roofing Materials
- Composition Shingles: Most popular in North America, 3-bundle packages typically cover 100 ft² (1 square)
- Roll Roofing: Economical option for low-slope roofs, comes in 36-inch wide rolls
- #15 Felt Paper: Lightweight underlayment, provides moisture barrier under shingles
- #30 Felt Paper: Heavier underlayment, better for steep roofs and severe weather
- Ceramic/Clay Tiles: Durable and long-lasting, but heavy and require special calculations
- Metal Roofing: Lightweight and durable, measured differently than shingles
Tips for Using Roofing Calculator
- Always add 10% buffer for waste, cuts, and mistakes - complex roof shapes may need 15-20%
- Measure the base area of your house carefully - this is the footprint, not the roof surface
- Account for eaves overhang - typically 6-18 inches beyond the wall
- For complex roofs with multiple sections, calculate each section separately and add them together
- Consider roof features like dormers, valleys, and chimneys - they increase material needs
- Check local building codes - some areas require specific underlayment or materials
- Order materials from the same batch to ensure color consistency
- Steeper roofs are more difficult to work on - factor in higher labor costs
- Plan for flashing around chimneys, vents, and roof edges
- Consider weather - roofing work requires dry conditions
About Roofing
Roofing is one of the most critical components of any building, protecting the structure and occupants from weather elements. A typical asphalt shingle roof lasts 15-30 years depending on quality and climate. The roof system consists of several layers: decking (plywood or OSB), underlayment (felt paper), and the finish roofing material. Proper ventilation is essential to prevent moisture buildup and extend roof life. When replacing a roof, consider upgrading insulation and ventilation at the same time. Professional installation is recommended for safety and warranty purposes, though DIY is possible for experienced builders.