Estimate Shingles for Your Roof
Roofing materials are sold in "squares," where one square covers 100 square feet of roof. This roofing calculator starts with the building's footprint, applies a pitch multiplier to account for the roof's slope, and adds a waste factor. It then shows the roof area, the number of squares, the shingle bundles needed and an estimate of ridge caps for gable roofs.
How the Roof Area Is Calculated
Roof area = length × width × pitch multiplier × (1 + waste % ÷ 100). Squares = roof area ÷ 100. Bundles = squares × 3, because most architectural shingles come 3 bundles per square.
Pitch multipliers: 2/12 = 1.028, 4/12 = 1.054, 6/12 = 1.118, 8/12 = 1.202, 10/12 = 1.302, 12/12 = 1.414.
Example: a 40 ft × 30 ft house (1,200 sq ft footprint) with a 6/12 pitch and 10% waste has about 1,476 sq ft of roof. That is 14.8 squares, or 45 bundles.
How to Find Your Roof Pitch
Roof pitch is the rise in inches for every 12 inches of horizontal run. Hold a level horizontally against the roof (or a rafter in the attic), measure 12 inches along it, and then measure straight up to the roof. If that distance is 6 inches, your pitch is 6/12.
Frequently Asked Questions
What is a square in roofing?
A roofing square is 100 square feet of roof surface. A typical bundle of architectural shingles covers about one-third of a square, so 3 bundles make one square.
How much waste should I add for roofing?
About 10% is standard for simple gable roofs. Hip roofs, valleys, dormers and other complex designs often need 15% or more because of extra cutting.
Should I include the overhang in my measurements?
Yes. For an accurate estimate, measure the roof edge to edge including eaves and overhangs, not just the walls of the house.