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.
Roof slope area formula.
Outside of the u s a degree angle is typically used.
A 12 in 12 pitch is a steep 45 degree angle roof.
Rafter rise run this formula is from the pythagorean theorem.
Take the area of the roof s footprint say it s 5 000 square feet and multiply 5 000 by 1 118.
To accurately calculate the area of your roof you must first determine its slope or pitch.
This will give you the rise over run or pitch.
For example if your roof s pitch is 4 in 12 you would divide 4 by 12.
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.
A roof s pitch is determined by how much it rises vertically for every foot it runs horizontally.
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.
If your number is 1 3 squared would yield 1 9.
Tan 45o 1 00.
In civil engineering the slope is the numerical measure of the steepness of a roof.
And that s the number you were looking for.
For example if you measure 4 inches the pitch of your roof is 4 12.
Roof pitch is a determining factor for cost of the roof as well as the roof area and the type of materials used.
And for a roof with a slope of 6 12 that number 1 118 is your roof slope multiplier.
Measure from an exterior wall to an exterior wall and divide by two.
Calculating the area true if you want to get the exact area measurement for your roof you can follow these steps.
Multiply the result by the factor and this is the length of the roof from base to ridge.
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.
You can also calculate roof pitch even without using a roof slope calculator.
Now you re ready to price out the materials.
Thus a moderate 6 in 12 roof pitch means that the roof rises 6 inches vertically for every 12 horizontal inches it runs.
Use the factor instead.
Use the following formula which also describes a right triangle.
That gives you 5 590 square feet which is the actual area of the surface of the roof.
In the imperial unit of measurements the slope is expressed with the rise and run.
Roof slope is also called as roof pitch.
This would yield 1 3 next square your result.
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.
