Roof Calculator

Estimate total roof area (both slopes), pitch, and optional material/costs. Supports metric & imperial units.

Building Length

Building Width

Eave Overhang (adds to length, both sides)

Gable Overhang (adds to width, both sides)

Roof Pitch

Degrees

Slope (rise / run)

Run default is 12 (in or any unit)

Waste allowance (%)

Display Area In

Material (optional)

Cost per area (optional)

Results

Plan Area	Pitch Factor	Angle	Total Area	Total Area + Waste

Formula: Total Roof Area = Plan Area × Pitch Factor. For a simple gable roof (two slopes), Plan Area = (Length + 2×Eave Overhang) × (Width + 2×Gable Overhang).
Pitch factor = sec(θ) = 1 / cos(θ) = √(1 + (rise/run)²).

What is a Roof Calculator?

A roof calculator is a practical tool for estimating roof area, pitch (slope), material requirements, and overall surface coverage. It helps homeowners, architects, and builders quickly calculate roofing dimensions without manual formulas, reducing errors and saving time during planning.

What is Roof Pitch?

The roof pitch (or slope) is the angle of the roof surface compared to the horizontal plane. It is commonly expressed as a ratio (e.g., 4:12, meaning 4 units of rise for every 12 units of run) or as a percentage. Roof pitch affects not only the appearance but also drainage, snow load, and material usage.

Why Use a Roof Calculator?

Material Estimation: Calculate how many shingles, tiles, or metal sheets are required.
Cost Planning: Estimate roofing costs more accurately before starting a project.
Time Saving: Avoid manual geometry calculations when planning roof construction.
Architectural Design: Check how different pitches and dimensions affect total surface area.

How to Use

Enter your roof dimensions (length, width, and overhang if needed).
Select or input the roof pitch (in degrees or ratio, e.g., 6:12).
The calculator will compute the roof surface area.
Optionally, enter shingle/tile size or cost to estimate required materials and expenses.

Example Calculations

Gable Roof with 8:12 pitch: A house 10 m × 8 m with a gable roof and 0.3 m overhang will have approximately ~110 m² roof surface area.

Shingle Estimate: If one bundle of shingles covers 3 m², you would need about 37 bundles for this roof.

Want to calculate roof trusses? Try our Roof Truss Calculator →