How it works
Measure the house footprint including eave and rake overhangs, choose the pitch, and the calculator converts the flat footprint into actual sloped roof area using the pitch multiplier. Roofing is priced by the square, which is 100 sq ft of roof surface.
Pitch is the rise in inches for every 12 inches of horizontal run. A 6/12 roof is about 12% larger than its footprint; a 12/12 roof is about 41% larger. The multiplier works for any roof with a single pitch, gable or hip.
Most architectural shingles come 3 bundles to the square. Add 10% waste on a simple gable and 15% or more on hip roofs and roofs with valleys and dormers, then add starter strip and ridge cap.
Formula
Roof area = footprint × √(1 + (pitch ÷ 12)²). Squares = roof area × (1 + waste) ÷ 100. Bundles = squares × 3.
Questions people ask
How many bundles of shingles are in a square?
Three for most standard three-tab and architectural shingles. Some heavy designer shingles are 4 or 5 bundles per square; check the wrapper.
How do I find my roof pitch?
Hold a level horizontally against the roof or a rafter, measure 12 inches along it, then measure straight up to the roof surface. That rise in inches is the pitch over 12.
Does a hip roof need more shingles than a gable?
At the same pitch and footprint the surface area is the same, but hips create more cut waste and need more ridge cap. Use about 15% waste instead of 10%.
How many squares is a 2,000 sq ft house?
It depends on the footprint and pitch, not the living area. A single-story 2,000 sq ft house with 1 ft overhangs and a 6/12 roof is about 24 squares before waste.