Roofing Calculators
Roof Area Calculator
Calculate your true sloped roof area from building dimensions and roof pitch. Get results in square feet, square metres, and roofing squares with adjustable waste factor.
Enter Dimensions
Results update automatically as you change inputs.
Roof Area Visualization
Footprint Area
80.00 m²
861.11 ft²
Sloped Roof Area
86.84 m²
934.75 ft²
Area with Waste (10%)
95.52 m²
1,028.22 ft²
Roofing Squares
10.28
1 square = 100 ft² (9.29 m²)
Pitch Multiplier Used
1.0541
Pitch Angle
18.43°
Area Increase
+5.41%
Calculation Breakdown
Pitch Multiplier Reference Table
Multiply your footprint area by the pitch multiplier to get the true sloped roof area.
| Pitch Ratio | Angle (°) | Multiplier | Area Increase |
|---|---|---|---|
| 1:12 | 4.76° | 1.0035 | +0.3% |
| 2:12 | 9.46° | 1.0138 | +1.4% |
| 3:12 | 14.04° | 1.0308 | +3.1% |
| 4:12 | 18.43° | 1.0541 | +5.4% |
| 5:12 | 22.62° | 1.0833 | +8.3% |
| 6:12 | 26.57° | 1.1180 | +11.8% |
| 7:12 | 30.26° | 1.1577 | +15.8% |
| 8:12 | 33.69° | 1.2019 | +20.2% |
| 9:12 | 36.87° | 1.2500 | +25.0% |
| 10:12 | 39.81° | 1.3017 | +30.2% |
| 11:12 | 42.51° | 1.3566 | +35.7% |
| 12:12 | 45.00° | 1.4142 | +41.4% |
Roof Pitch Calculator
Find your roof pitch from rise and run measurements. Get pitch ratio, degrees, and slope percentage.
Calculate Roof Pitch →Roofing Squares Calculator
Convert roof area to roofing squares for accurate material ordering with waste factor adjustment.
Calculate Roofing Squares →All Roofing Calculators
Browse our full suite of free roofing calculators for every roof type and measurement need.
View All Calculators →Frequently Asked Questions
Common questions about calculating roof area
How do I calculate my roof area?
Measure your building's length and width to get the footprint area. Then multiply by the pitch multiplier for your roof slope. For example, a 10m × 8m building with a 22.5° pitch has a footprint of 80m² and a sloped area of approximately 86.8m².
What is a roofing square?
A roofing square is a unit of measurement equal to 100 square feet (approximately 9.29 square metres) of roof area. Roofing materials are often sold by the square.
How much extra material should I order for waste?
For simple gable roofs, add 10-15% for waste. For hip roofs, add 15-20%. For complex roofs with many valleys and hips, add 20-25%. Our calculator includes an adjustable waste factor.
Does roof pitch affect the total area?
Yes. Steeper roofs have more surface area than the building footprint. A 45° (12:12) pitch roof has 41.4% more area than the flat footprint. Even a moderate 22.5° pitch adds about 8.2%.
How do I find my roof pitch?
Use our roof pitch calculator or measure directly: from inside the attic, place a level horizontally from a rafter, measure 300mm along the level, then measure the vertical distance down to the rafter.
Can I calculate roof area from Google Maps?
Google Maps gives you the footprint area (bird's eye view), not the sloped area. You still need to apply the pitch multiplier. Enter the footprint dimensions in our calculator and select your pitch to get the true sloped area.
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