Roofing Calculator
Calculate roof squares, total square footage, and material needed with waste factor for any roof pitch.
Squares (with waste)
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Total Sq Ft
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Base Squares
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Pitch Factor
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What is Roofing Calculator?
The Roofing Calculator estimates the total roof area and number of roofing squares needed for a gable roof. It accounts for roof pitch using a pitch factor multiplier and adds a user-defined waste percentage for cuts and overlaps. One roofing square equals 100 square feet.
How to use
- 1 Enter the roof length and width (the footprint dimensions of the building).
- 2 Select the roof pitch from the dropdown (rise over 12-inch run).
- 3 Enter a waste percentage — typically 10% for simple roofs, 15% for complex ones.
- 4 Click Calculate to see total squares, square footage, and squares with waste.
- 5 Order at least the 'with waste' amount to ensure you have enough material.
Formula
Example calculation
A 40 × 30 ft roof with a 6/12 pitch and 10% waste: footprint = 1200 sq ft. Roof area = 1200 × 1.118 = 1341.6 sq ft = 13.4 squares. With 10% waste = 14.8 squares (order 15).
Frequently asked questions
What is a roofing square?
One roofing square equals 100 square feet. Shingles and other roofing materials are typically sold by the square.
How many bundles of shingles per square?
Standard three-tab shingles come 3 bundles per square. Architectural (dimensional) shingles may require 4 bundles per square — check the manufacturer's spec.
What pitch factor should I use?
Measure the rise (vertical inches) per 12 inches of horizontal run. A 6/12 pitch rises 6 inches for every 12 inches of run.
Why add waste percentage?
Cutting shingles around valleys, ridges, hips, and edges produces offcuts that cannot be reused. 10–15% is a standard allowance.
Does this include ridge cap or underlayment?
No — this calculates field shingles only. Ridge cap and underlayment are ordered separately based on the ridge length and total area.