About the roofing calculator
A sloped roof has more surface than the footprint it covers. This calculator multiplies your footprint by a pitch factor to find the real roof area, then converts it to squares — the roofing industry’s unit of 100 square feet — and to bundles using the figure on your shingle packaging.
How to use this calculator
- Measure the footprint including overhangs.
- Choose the roof pitch (rise per 12 inches of run).
- Choose a waste allowance.
- Enter bundles per square from the shingle label.
Worked examples
- Pitch factor: √(1 + 0.25) = 1.118
- Roof area: 2,236 sq ft
- With 10% waste: 2,460 sq ft = 24.6 squares
- 3 bundles per square: 73.8
About 24.6 squares, or 74 bundles.
Measurement guidance
Finding the pitch
Pitch is the vertical rise over 12 inches of horizontal run. It’s often listed on house plans, or a roofer can measure it safely.
Safety
Measuring from the ground or from plans is safer than climbing on a roof.
Frequently asked questions
What is a roofing square?
100 square feet of roof surface.
How many bundles are in a square?
It depends on the shingle product; check the packaging.
Does this include ridge caps and underlayment?
No. Those are separate items.