Take the area of the roof s footprint say it s 5 000 square feet and multiply 5 000 by 1 118.
Multiplier for 3 12 roof.
It affects walkability as well as drainage and roofs in areas of high rain.
800 multiplied by 1 16.
Multiply 20 and 40 which equals 800.
We excluded roof multipliers for pitch below 3 and above 12 for the following reasons.
That gives you 5 590 square feet which is the actual area of the surface of the roof.
This will give you the rise over run or pitch.
We included a roof pitch chart below the 7 12 example image and the calculator below that.
If this isn t practical then perform the same measurement on the underside of the roof.
Outside of the u s a degree angle is typically used.
For instance a 7 12 roof pitch means that the roof rises 7 inches for every 12 horizontal inches.
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 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.
For example a 4 12 pitch roof that is 100 square feet.
Use our roof pitch calculator to find the pitch of your roof.
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 the home measures 20 x 40 and has a 7 12 roof then to calculate the slope of the roof follow these steps.
Now divide the rise by the multiplier to get the pitch eg.
The calculator above can handle much of this math.
Roof pitch area multipliers.
The pitch of this roof is 4 8 12.
Roof pitch is a determining factor for cost of the roof as well as the roof area and the type of materials used.
Get your roof size by using this roof pitch calculator.
For example if you measure 4 inches the pitch of your roof is 4 12.
Find the value of 7 12 from the roof slope multiplier table which is 1 16.
Roof pitch degree table.
Multiply step 1 and step 2 i e.
100 1 054 105 4ft 2.
The pitch of the roof is the rise over a 12 inch run.
And for a roof with a slope of 6 12 that number 1 118 is your roof slope multiplier.
48 10 4 8.
With pitch under 3 you can easily walk on the roof to get the exact measurements as that is usually a flat roof.
Next multiply the footprint of the roof by the multiplier below for your roof pitch to find the overall roof area.
Also the multiplier is so close to one that it does not really change the total size unless your roof is something like a 100 100.
Roof is 6 12 pitch and measures at 2 400 square feet so 2400 x 1 12 2 688 2 88 sqs added for pitch.
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.
