Roof Area Calculator
Calculate actual roof area from house dimensions, pitch, and roof type. Get accurate square footage, roofing squares, and bundle counts.
How It Works
Enter house footprint
Measure the exterior length and width of your home at ground level.
Select roof type & pitch
Choose gable, hip, or shed roof and enter your rise-over-run pitch.
Get area and squares
Receive actual roof area, roofing squares, bundle count, and waste estimate.
Frequently Asked Questions
How do I calculate roof area?
Multiply the house footprint length by width to get the base area, then multiply by the pitch multiplier for your roof slope. For a 6/12 pitch the multiplier is 1.118. Then add 10–20% for waste. Divide the total by 100 to get roofing squares. Example: 40 ft × 50 ft = 2,000 sq ft × 1.118 = 2,236 sq ft ÷ 100 = 22.4 squares.
What is a roofing square?
A roofing square equals 100 square feet of roof surface. It is the standard unit roofing contractors use for pricing. Most shingles come 3 bundles per square. To calculate squares: divide your total roof area (in sq ft) by 100. A 2,500 sq ft roof = 25 squares.
How many bundles of shingles per square?
Standard 3-tab and architectural shingles typically come 3 bundles per square (each bundle covers about 33 sq ft). Some premium shingles come 4 bundles per square. Always check the manufacturer specifications on your specific shingle brand, as coverage can vary.
Do I need to add a waste factor to my roof area?
Yes. Always add a waste factor to your calculated roof area. Use 10% for simple gable roofs. Use 15% for roofs with one or two valleys or hips. Use 20% for complex roofs with multiple valleys, dormers, or steep pitches. The waste accounts for cuts at edges, hips, valleys, and around penetrations.