To convert between american roofing ratios and pitch degrees follow these steps.
12 12 roof pitch multiplier.
A 12 12 pitch roof has a pitch angle of 45.
Multiply 20 and 40 which equals 800.
The pitch of this roof is 4 8 12.
If the home measures 20 x 40 and has a 7 12 roof then to calculate the slope of the roof follow these steps.
Image 1 12 to 12 12 roof pitch 7 12 pitch.
Why figure what your roof pitch is.
Get your roof size by using this roof pitch calculator.
So 2400 x 1 12 2 688 2 88 sqs added for pitch.
What is the multiplier.
Then the roof multiplier is.
Multiply step 1 and step 2 i e.
For example if you measure 4 inches the pitch of your roof is 4 12.
48 10 4 8.
The calculator above can handle much of this math.
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.
Using the pythagorean theorem we find that for every 12 inches the roof spans horizontally there are 13 inches of actual roof.
Divide the first part of the ratio by 12 to work out the pitch.
If this isn t practical then perform the same measurement on the underside of the roof.
The value arrived at 928 reflects the square feet of the roof.
Roof is 6 12 pitch and measures at 2 400 square feet.
Roof pitch degree table.
For example a roof with a pitch of 1 cannot use metal shingles.
Now divide the rise by the multiplier to get the pitch eg.
Helps determine what materials are suitable for your roof.
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.
This will give you the rise over run or pitch.
Roofers typically refer to it as a pitch and can be found by factoring the rise over a 12 inch run.
We included a roof pitch chart below the 7 12 example image and the calculator below that.
Roof pitch multiplier 13 over 12 1 08.
Find the inverse tangent of the pitch to find the angle in degrees.
800 multiplied by 1 16.
A flat roof has a pitch of 1 meaning the material needed is 1.
Find the value of 7 12 from the roof slope multiplier table which is 1 16.
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.
Once you know the roof slope multiplier for a particular slope you can use it to find the actual area of any size sloped roof with the same slope.
