Steep roofs measure your house at ground level then add in the roof s overhang for greater accuracy.
Formula roof pitch multiplier.
Step 3 multiply step 1 and step 2 i e.
100 1 054 105 4ft2.
A roof pitch multiplier also called a roof pitch factor is a number that is multiplied by the area covered by a sloped roof to produce the area of the actual surface of the roof.
Pitch rise run 1 5 6 25.
Calculate the roof pitch as the proportion of rise and run.
Where a is the rise of the roof b is the run of the roof and c is the rafter hypotenuse of the triangle with side lengths a and b.
Here are the equations you may use to solve for the length of the slope and the rafter.
For example a 4 12 pitch roof that is 100 square feet.
The calculator above can handle much of this math.
Next multiply the footprint of the roof by the multiplier below for your roof pitch to find the overall roof area.
Since pitch is the rise over a 12 inch run divide the run by 12 to get the multiplier in this case 120 12 10.
Roof pitch degree table.
Let s say it is equal to 1 5 m.
The pitch of this roof is 4 8 12.
48 10 4 8.
Measure the rise of your roof.
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.
Calculate the rafter length substituting these values into the following formula.
Step 1 multiply 20 and 40 which equals 800.
For roof slopes expressed as x in 12 rise in run the roof pitch multiplier is determined by finding the square root of rise run 1.
800 multiplied by 1 16.
Rafter rise run 1 5 6 2 25 36 38 25rafter 38 25 6 18 m.
Image 1 12 to 12 12 roof pitch 7 12 pitch.
Use the following formula which also describes a right triangle.
Use our roof pitch calculator to find the pitch of your roof.
Rafter rise run this formula is from the pythagorean theorem.
If the home measures 20 x 40 and has a 7 12 roof then to calculate the slope of the roof follow these steps.
Step 2 find the value of 7 12 from the roof slope multiplier table which is 1 16.
Now solving for c in the equation above gives.
You can also calculate roof pitch even without using a roof slope calculator.
Now you re ready to price out the materials.
