Roofing Calculator
Estimate roofing squares, bundles and underlayment.
Roofing is measured in squares: one square equals 100 sq ft of roof surface. Multiply the building footprint by the pitch factor—1.06 for 4:12, 1.12 for 6:12, or 1.25 for 9:12—to calculate the actual roof area. Divide that area by 100, then add 10%–15% for waste, hips, and valleys. Enter your dimensions to estimate roofing squares and shingle bundles.
Squares
13.42
1,342 ft²
Shingle bundles
41
3 bundles / square
Underlayment rolls
4
400 ft² rolls
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Recommended tools & materials
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Roofing Nailer
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How does the roofing calculator work?
Roof area = house footprint × pitch factor. The pitch factor is √(1 + (rise/12)²): a 6:12 roof has a 1.118 factor. A "square" is 100 ft² of roof. Shingles are sold in 3 bundles per square.
Which guide explains this in more depth?
- Panel roofs waste differently from shingles: ribs, hips and valleys all change the number you order. Read the metal roofing calculator waste factor guide for the full worked example.
What do people use the roofing calculator for?
Roofing for a House
Estimate shingle bundles and squares for a full re-roof.
Roofing for a Garage
Estimate shingle bundles and squares for a garage roof.
Roofing for a Shed
Estimate shingle bundles for a shed roof.
Roofing for a Porch
Estimate materials for a porch or overhang roof.
Roofing for an Addition
Estimate materials for a room-addition roof.
What else do people ask about this calculator?
How many bundles of shingles do I need?
3 bundles per roofing square. For a 40×30 ft home with a 6:12 roof: about 13.4 squares × 3 = 41 bundles.
What is a roofing square?
100 ft² of roof surface. Shingles are priced per square and packaged in bundles that cover ~33 ft² each.
Which related calculators should I use next?
All calculators
Complete Your Roofing Project
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