Roofing Shingle Calculator
Enter the roof footprint including overhangs and the pitch. The calculator converts the flat footprint to sloped roof area and gives the number of squares and shingle bundles.
Result
- Footprint area
- 1,200 sq ft
- Pitch multiplier
- 1.118
- Roof angle
- 26.57°
- Area with waste
- 1,475.8 sq ft
This applies to gable, hip and shed roofs with one pitch. Complex roofs with dormers or several pitches should be measured section by section.
Formula
- Pitch multiplier = √(1 + (pitch ÷ 12)²)
- Roof area = footprint area × pitch multiplier
- Squares = roof area ÷ 100
- Bundles = squares × 3 for most three-tab and architectural shingles
How the Roofing Shingle Calculator works
A sloped roof has more surface than the ground it covers. For any roof with a single pitch, the surface area equals the horizontal footprint multiplied by a factor that depends only on the pitch. A 6 in 12 pitch has a factor of 1.118.
Roofing is sold by the square, which is 100 square feet of roof. Most shingles are packaged three bundles to a square. Add 10 percent for a simple gable roof and 15 percent for hips and valleys.
Worked example
A 40 ft × 30 ft footprint is 1,200 sq ft. At a 6 in 12 pitch the multiplier is 1.118, so the roof area is 1,341.6 sq ft. With 10 percent waste that is 1,475.8 sq ft, or 14.76 squares, which takes 45 bundles.
Frequently asked questions
What is a roofing square?
One square is 100 square feet of roof surface. A 1,500 square foot roof is 15 squares.
How many bundles of shingles are in a square?
Three bundles for most three-tab and architectural shingles. Some heavy designer shingles need four or five, so check the wrapper.
How do I find my roof pitch?
Hold a level horizontally against the roof, measure 12 inches along it, and measure straight down to the roof at that point. That drop in inches is the pitch.
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