If the home measures 20 x 40 and has a 7 12 roof then to calculate the slope of the roof follow these steps.
12 12 roof pitch multiplier.
We included a roof pitch chart below the 7 12 example image and the calculator below that.
Then the roof multiplier is.
To convert between american roofing ratios and pitch degrees follow these steps.
If this isn t practical then perform the same measurement on the underside of the roof.
Multiply step 1 and step 2 i e.
Divide the first part of the ratio by 12 to work out the pitch.
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.
Find the value of 7 12 from the roof slope multiplier table which is 1 16.
Roof pitch degree table.
Now divide the rise by the multiplier to get the pitch eg.
So 2400 x 1 12 2 688 2 88 sqs added for pitch.
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.
Using the pythagorean theorem we find that for every 12 inches the roof spans horizontally there are 13 inches of actual roof.
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.
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.
Find the inverse tangent of the pitch to find the angle in degrees.
Get your roof size by using this roof pitch calculator.
Image 1 12 to 12 12 roof pitch 7 12 pitch.
A flat roof has a pitch of 1 meaning the material needed is 1.
800 multiplied by 1 16.
This will give you the rise over run or pitch.
Helps determine what materials are suitable for your roof.
For example a roof with a pitch of 1 cannot use metal shingles.
Multiply 20 and 40 which equals 800.
So in this case for every 12 inches the roof goes across horizontally b while rising 6 inches a there s actually 13 416 inches of roof c.
For example if you measure 4 inches the pitch of your roof is 4 12.
C sqrt 5 2 12 2 sqrt 169 13 in.
48 10 4 8.
What is the multiplier.
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.
The value arrived at 928 reflects the square feet of the roof.
A 12 12 pitch roof has a pitch angle of 45.
Roofers typically refer to it as a pitch and can be found by factoring the rise over a 12 inch run.
The pitch of this roof is 4 8 12.
Roof is 6 12 pitch and measures at 2 400 square feet.
