Roofing Calculator
Estimate roof area in 'squares' and how many bundles of shingles you need.
How to use this tool
- Enter the building footprint (length x width, or total flat area).
- Set the roof pitch (rise over run, e.g. 6/12).
- Add overhang if included.
- Set bundles per square (default 3).
- Add wastage and calculate squares and bundles.
How it works
Footprint area x pitch multiplier = roof area. Squares = roof area / 100. Bundles = squares x bundles-per-square, plus wastage (default 10%).
Tips
- Measure from the exterior wall line for the footprint.
- Hip and valley roofs need extra for cuts — raise wastage to 15%.
- Order all bundles at once for color matching.
Limitations
Multi-plane roofs need each plane entered; dormers and valleys add complexity the calculator approximates via wastage.
Frequently asked questions
What is a roofing square?
One square = 100 sq ft of roof surface. Roofers price by the square, so knowing your square count is step one.
How does roof pitch affect area?
A steeper roof has more surface for the same footprint. The pitch multiplier (e.g., 6:12 ≈ 1.12×) converts footprint area to roof area.
How many bundles per square?
Typically 3 bundles of asphalt shingles per square (each covers ~33 sq ft). Slate and metal differ — the calculator lets you choose.