Roofing Calculator
Estimate the surface area of a roof from its footprint and pitch, and convert it into roofing squares and shingle bundles for planning and budgeting.
Include the eaves overhang.
Include the gable overhang.
About 10% for simple gable roofs; 15% or more for hips and valleys.
3 is typical for asphalt shingles — check the wrapper.
Roof area = footprint × pitch factor, where pitch factor = √(1 + (rise ÷ 12)²). One roofing square covers 100 sq ft. This assumes a single pitch over the whole roof and doesn't count ridge caps, starter strips, underlayment or flashing — it's an estimate for planning, not a roofing quote.
1,677 sq ft
Roof surface area
× 1.118
Pitch factor
18.45
Squares incl. 10% waste
56
Shingle bundles
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How to use roofing calculator
- 1Choose units and whether to enter the footprint's length and width or its total area.
- 2Enter the footprint, including overhangs at the eaves and gables.
- 3Select the roof pitch — the rise in inches for every 12 inches of horizontal run.
- 4Set a waste allowance and bundles per square, then read the area, squares and bundles.
About this tool
A sloped roof has more surface area than the ground it covers. The calculator multiplies the footprint by a pitch factor of √(1 + (rise ÷ 12)²): about 1.054 for a 4/12 pitch, 1.118 for 6/12 and 1.414 for 12/12. Roofing materials are commonly sold by the “square”, which covers 100 sq ft of roof.
Example: a 50 × 40 ft footprint (2,000 sq ft) with a 6/12 pitch has about 2,236 sq ft of roof surface — 22.4 squares. With 10% waste that's 24.6 squares, or 74 bundles of standard asphalt shingles at 3 bundles per square.
This is an estimate, not a roofing quote. It assumes a single pitch across the whole roof and doesn't count ridge caps, starter strips, underlayment, flashing or ventilation. Complex roofs with hips, valleys and dormers need more waste — 15% or more. Measuring on a roof is dangerous; use plans, the footprint from the ground, or a professional survey.
Frequently asked questions
A unit of roof area equal to 100 square feet (about 9.29 m²). A 2,500 sq ft roof is 25 squares.
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