Roofing calculator
Estimate the roof area, roofing squares and shingle bundles for a gable or hip roof from its pitch.
About this calculator
Enter the building length and width, any overhang, and the roof pitch as a rise in 12 or in degrees. The calculator multiplies the footprint by a slope factor, adds a waste allowance, and converts to roofing squares and bundles.
Always confirm a final order with your roofer, as dormers, valleys and chimneys change the total.
Measurements and terms explained
- Pitch (rise in 12)
- How many inches the roof rises for every 12 inches it runs horizontally.
- Slope factor
- The number that turns flat footprint area into true sloped roof area. A 6 in 12 pitch has a factor of 1.118.
- Overhang
- How far the roof extends past the wall on each side.
- Waste allowance
- Extra material for cuts, hips and ridges. 10 to 15% is typical.
- Bundle
- One pack of shingles, covering about a third of a square.
Common questions
What is a roofing square?
100 square feet of roof. Shingles are sold by the square, usually three bundles to a square.
What pitch is my roof?
Measure how many inches the roof rises over 12 inches of horizontal run. A 6 in 12 pitch is about 26.6 degrees.
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