Roofing Calculator
What is the roof pitch?
Roof pitch is simply the slope created by the rafter. It can be assessed in two ways  either as the angle the rafter makes with the horizontal or the proportion between the rise and the run of the roof.
Roof pitch is often expressed as a ratio between rise and run in the form of x:12. For example, a pitch 1:12 means that per every twelve yards of building length the rise will be equal to one yard.
We can divide roofs into the following categories:

Flat roofs are not perfectly flat in reality  they need a small slope for water runoff. Generally, these roofs have a pitch from 1/2:12 to 2:12 (from 4.2% to 16.7%).

Low pitched roofs have the pitch below 4:12 (33.3%). These are generally difficult in maintenance, as they require special materials to avoid leaks.

Conventional roofs have the pitch ranging from 4:12 to 9:12 (33.3% to 66.7%). They are the easiest ones to construct and they are safe to walk on.

Highpitched roofs often require additional fasteners. They have a pitch that can be as high as 21:12 (175%).
How to calculate roof pitch?
Generally, roof pitch is calculated from the same formula that describes a right triangle. You can use the following equations to find the length of the rafter and the slope:

rafter² = rise² + run² (from the Pythagorean theorem);

rise / run = pitch, where pitch is expressed in percent;

pitch = tan (angle), where angle is the roof pitch expressed in degrees.
If you want to find the roof pitch in the form of x:12, simply calculate the pitch and substitute 12 for the run length. The value displayed as the rise will be your x.
How to calculate roof pitch?
Generally, roof pitch is calculated from the same formula that describes a right triangle. You can use the following equations to find the length of the rafter and the slope:

rafter² = rise² + run² (from the Pythagorean theorem);

rise / run = pitch, where pitch is expressed in percent;

pitch = tan (angle), where angle is the roof pitch expressed in degrees.
If you want to find the roof pitch in the form of x:12, simply calculate the pitch and substitute 12 for the run length. The value displayed as the rise will be your x.
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