Roof Slope Area Formula

Use the following formula which also describes a right triangle.

Roof slope area formula.

A 12 in 12 pitch is a steep 45 degree angle roof. Once you have your roof s pitch divide the number by 12. For example if you measure 4 inches the pitch of your roof is 4 12. Tan 45o 1 00.

This will give you the rise over run or pitch. Roof pitch is a determining factor for cost of the roof as well as the roof area and the type of materials used. This would yield 1 3 next square your result. Calculating the area true if you want to get the exact area measurement for your roof you can follow these steps.

Take the area of the roof s footprint say it s 5 000 square feet and multiply 5 000 by 1 118. As a sanity check we confirm that the tangent of 45 degrees is 1 or that two opposed 45 degree or 12 in 12 slope roof surfaces will form a 90 degree angle where they meet at the ridge and will form 45 degree angles where they meet the wall top plate or with respect to any horizontal line in the building. Multiply the result by the factor and this is the length of the roof from base to ridge. Take your area result and multiply it by the pitch multiplier or slope correction factor found in the table above to arrive at the roof s surface area.

Now you re ready to price out the materials. If your number is 1 3 squared would yield 1 9. You don t have to climb a ladder and place a tape measure on the ridge and measure down to the base to find the length of the roof. Outside of the u s a degree angle is typically used.

See the image below for more explanation on rise run and pitch. And for a roof with a slope of 6 12 that number 1 118 is your roof slope multiplier. In civil engineering the slope is the numerical measure of the steepness of a roof. In the imperial unit of measurements the slope is expressed with the rise and run.

Roof slope is also called as roof pitch. For example if your roof s pitch is 4 in 12 you would divide 4 by 12. And that s the number you were looking for. Use the factor instead.

Simply locate a roof rafter board place the end of the level against the bottom edge and measure from the 12 inch mark vertically to the bottom edge of the rafter. A roof s pitch is determined by how much it rises vertically for every foot it runs horizontally. To accurately calculate the area of your roof you must first determine its slope or pitch. For instance a 7 12 roof pitch means that the roof rises 7 inches for every 12 horizontal inches.

Here are the equations you may use to solve for the length of the slope and the rafter. By slope angle formula steepness can be obtained by dividing vertical rise by horizontal span. That gives you 5 590 square feet which is the actual area of the surface of the roof. Measure from an exterior wall to an exterior wall and divide by two.