Roofing Calculator
Calculate the total roof area for gable, hip, or flat roofs. Get roofing material quantities in squares, sheets, and tiles with waste allowance.
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How to use this calculator
Roof area is always larger than the floor footprint because of the pitch. A steeper pitch increases the roof area and material required.
- 1
Enter the building length and width (not including overhang).
- 2
Select the roof type and enter the pitch angle in degrees.
- 3
Enter eave overhang on each side (typically 0.3–0.6 m).
- 4
Enter the roofing sheet or tile area to get a sheet count.
Frequently asked questions
What is a roofing square?
A roofing square is 100 square feet (9.29 m²). It is the standard unit used in the roofing industry, particularly for asphalt shingles in the US and Australia. Tiles and corrugated sheets are typically sold by the sheet or by m².
How do I convert roof pitch to degrees?
Pitch is often expressed as rise/run (e.g., 4/12 means 4 inches rise per 12 inches run). To convert: degrees = arctan(rise/run) × (180/π). 4/12 pitch ≈ 18.4°; 6/12 ≈ 26.6°; 8/12 ≈ 33.7°; 12/12 (45°) is very steep.
How much waste should I allow for roofing?
Standard rectangular roof: 10%. Complex roofs with many hips, valleys, and penetrations: 15–20%. Tile or shingle waste at ridges and hips adds up quickly. Always round up to the nearest pack or square.
Roofing Calculator — Roof Area, Squares & Material Count
Roof pitch and material compatibility
Flat/low pitch (0–10°): requires waterproof membrane (TPO, EPDM, butynol). Low pitch (10–15°): Colorbond/metal sheeting. Moderate pitch (15–30°): most materials, including concrete/terracotta tiles and metal. Steep pitch (>30°): slate, clay tiles, asphalt shingles, cedar shakes. Always check manufacturer minimum pitch specifications.
Getting roofing quotes
Roofing contractors price by the square (100 sq ft / 9.29 m²) including labour and materials. Get at least three quotes for large roofs. The roofing calculator gives you the area so you can verify quotes and compare cost per m². Ask for a written breakdown of material cost, underlayment, ridge capping, guttering, and labour separately.
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Results are estimates for informational purposes only and do not constitute professional financial, medical, legal, or technical advice. Read full disclaimer →