Roofing calculator
For a simple rectangular house. Give it the outside wall dimensions and the pitch, and it adds the overhang, works out the sloped area and turns it into an order.
Squares to order
0 squares
How it works
footprint = (length + 2 x overhang) x (width + 2 x overhang) roof area = footprint x slope factor, where slope factor = sqrt(144 + pitch^2) / 12 squares = roof area / 100, plus waste bundles = squares x 3 (standard architectural shingles)
A hip roof has the same area as a gable of the same pitch, because every slope rises at the same rate. It needs more waste (15% is common) for the cuts along the hips, and more ridge cap. Underlayment assumes synthetic rolls covering 10 squares; check the roll you buy. Drip edge comes in 10 ft pieces and runs along the eaves and rakes.
Real roofs have dormers, valleys, porches and wings, and this simple model misses them. For those, measure every plane: trace it in the RoofTools editor or let the LiDAR measurement do it from the address.
What a square is
Roofers price and order by the square: 100 square feet of roof surface, measured along the slope. A 2,000 sq ft single-storey house with a 6/12 roof and 1 ft overhangs needs about 24 squares before waste. Most architectural shingles come three bundles to the square.
Choosing a waste factor
Use 10% for a plain gable roof and 15% for a hip roof or one with valleys. Go to 20% for a cut-up roof with many dormers or for shingles with a large exposure pattern. Waste covers the cut pieces at rakes, hips and valleys, plus starter and the odd damaged bundle.
More roof calculators
Skip the tape measure
Type an address and RoofTools measures the roof from public LiDAR: every plane's pitch, direction and sloped area, the total in squares, and sun and shade for a solar layout. Then you can fix any plane in the editor.
Want someone to do the job?
Tell us where and when, and we'll put you in touch with a roofer or solar installer near you. No account needed.