Roofing project estimator

Roofing Material Calculator

Convert roof area into estimated quantities of roofing packages, underlayment rolls, battens, fasteners and ridge caps. Include a waste allowance to plan purchases more realistically.

Enter your roof details

Enter the actual sloped roof surface area if you know it. Use product coverage figures from the packaging or manufacturer.

Roof surface area Enter the total sloped roof area, not just the building footprint.

Area and length units Coverage figures below must use the selected area unit.

Waste allowance (%) A common planning allowance is around 10%; complex roofs may need more.

Main roofing material This label identifies the material in your estimate.

Roofing product coverage

Roofing coverage per package (m²) Example: one shingle bundle might cover about 3 m². Check the actual product label.

Underlayment coverage per roll (m²) Use effective coverage after required overlaps, if specified by the manufacturer.

Optional supporting materials

Batten length per m² (m) Enter your planned linear length of battens per unit of roof area. Use 0 if not applicable.

Fasteners per m² Enter the required nails, screws or other fasteners per area unit. Use 0 if not applicable.

Total ridge length (m) Leave blank or enter 0 if you do not need a ridge-cap estimate.

Ridge length covered per cap (m) Use the coverage length of one ridge-cap piece. This is required even if ridge length is blank.

Reset

How the estimate works

The calculator adds waste to the roof area, then divides the adjusted area by the coverage of each product. Package counts are rounded up because materials are normally purchased in whole packages.

Adjusted area
Roof area × (1 + waste percentage ÷ 100)

Roofing packages
Round up (adjusted area ÷ area covered per package)

Underlayment rolls
Round up (adjusted area ÷ effective coverage per roll)

Supporting materials
Batten length and fastener counts are based on the rates you enter. Ridge caps are estimated separately from ridge length.

Before buying materials

Use the actual sloped roof surface area, including all roof sections.
Confirm package coverage and effective coverage after overlaps.
Allow for valleys, hips, dormers, cuts, breakage and roof complexity.
Follow the roofing system's installation instructions and local building requirements.
Verify batten spacing and fastener requirements for your chosen product.

Related area and building calculators

Use these tools to calculate roof dimensions or estimate other building materials.

Roof Area Calculator Estimate roof surface area. Roof Pitch Calculator Calculate roof pitch and slope. Wall Area Calculator Calculate wall surface area. Ceiling Area Calculator Calculate ceiling area for a room. Paint Area Calculator Estimate paintable surface area. Flooring Calculator Estimate flooring quantities and waste. Area Unit Converter Convert square metres, square feet and more. Length Unit Converter Convert lengths for building measurements.

Frequently asked questions

How much waste should I add for roofing?

The appropriate allowance depends on the roof's shape, the roofing material, installation pattern and the number of cuts. Ten percent is a common starting estimate, not a universal rule. Complex roofs or products with specific layout requirements may need a different allowance.

Does the calculator determine roof area from house dimensions?

No. Enter the total sloped roof surface area. A building's footprint area is usually smaller than its actual roof area because of the roof pitch, overhangs and roof geometry.

Are the package coverage values exact?

No. The initial values are examples for estimation. Replace them with the effective coverage stated by your roofing material and underlayment manufacturers. Overlaps, exposure, installation pattern and product size can change usable coverage.

Does the estimate replace a professional roofing takeoff?

No. It is a planning aid. Confirm quantities, ventilation, flashing, underlayment, fasteners and other system components against the manufacturer's specifications and your local building requirements before ordering.