Roof Square Footage Calculator
Calculate the total square footage of a roof based on building dimensions and roof pitch. Useful for roofing material estimation.
Published by:
isCalculator Editorial Team
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How to Use the Roof Square Footage Calculator
This calculator estimates the total roof surface area in square feet based on building dimensions, roof pitch, and overhang. All inputs must be in feet (imperial units).
- Enter Building Length & Width – Provide the horizontal dimensions of the building (e.g., 40 ft by 30 ft). Values must be positive numbers.
- Enter Roof Pitch – Input the rise in inches per 12 inches of run (e.g., 6 for a 6/12 pitch). Accepts values from 0 to 24, in 0.5 increments.
- Enter Overhang (optional) – Add the overhang length on each side in feet (e.g., 1 ft). Default is 0 if left blank.
- Click "Calculate Roof Area" – The total square footage will appear, along with a breakdown of the formula used.
Note: The calculator adds overhang to both sides of length and width, then multiplies by a pitch factor derived from the roof slope. Results are rounded to two decimal places.
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Frequently Asked Questions
Roof pitch is the rise in inches for every 12 inches of horizontal run. For example, a 6/12 pitch means the roof rises 6 inches per 12 inches.
Overhang is the part of the roof that extends beyond the walls. It is measured per side and added to the building dimensions.
This calculator assumes a simple gable roof (two sloping planes). For complex shapes, consult a professional.