Roof Square Footage Calculator

Roof Square Footage Calculator

Accurately estimate the total area and roofing squares needed for your project.

Flat (0/12) 1/12 Pitch 2/12 Pitch 3/12 Pitch 4/12 Pitch (Common) 5/12 Pitch 6/12 Pitch 7/12 Pitch 8/12 Pitch 9/12 Pitch 10/12 Pitch 11/12 Pitch 12/12 Pitch (45 deg)

5% (Simple Gable) 10% (Standard Hip) 15% (Complex / Valleys) 20% (Extreme Complexity)

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How to Calculate Roof Square Footage

Estimating the square footage of a roof is more complex than measuring a flat floor because of the roof pitch (slope). When a roof is slanted, its surface area is significantly larger than the ground footprint of the house. This calculator helps you convert ground-level measurements into actual surface area.

1. The House Footprint

Start with the total square footage of the ground area covered by the roof. This includes the living space, attached garages, and porches. If you have a simple rectangular home, multiply length by width. For L-shaped or T-shaped homes, divide the footprint into smaller rectangles, calculate each, and add them together.

2. Accounting for Pitch (Slope)

Roof pitch is expressed as a ratio of "rise over run." A 4/12 pitch means the roof rises 4 inches for every 12 inches it runs horizontally. The steeper the pitch, the higher the pitch multiplier. For example:

• 4/12 Pitch: Multiplier of 1.054
• 8/12 Pitch: Multiplier of 1.202
• 12/12 Pitch: Multiplier of 1.414

3. What is a "Roofing Square"?

In the roofing industry, materials like shingles and underlayment are measured in "squares." One roofing square is equivalent to 100 square feet. If your roof is 2,400 square feet, you have a "24-square" roof.

4. The Importance of Waste Factor

No roof is a perfect rectangle. You must account for cutting shingles around valleys, hips, gables, and chimneys. A standard gable roof typically requires a 5% to 10% waste factor, while a complex hip roof with many dormers might require 15% to 20% extra material to ensure you don't run out during installation.

Example Calculation

If your house footprint is 1,500 sq ft and you have a 6/12 pitch:

1. Find the multiplier for 6/12 pitch (1.118).
2. 1,500 x 1.118 = 1,677 sq ft (Surface Area).
3. Add 10% waste: 1,677 x 1.10 = 1,844.7 sq ft.
4. Convert to squares: 1,844.7 / 100 = 18.45 squares.