This roof pitch calculator is a handy tool that will help you quickly assess what is the pitch of your roof of what length of rafters you need for your construction works. We will explain to you how to determine the roof pitch step by step. You can also use this roof slope calculator to recalculate the roof pitch from degrees to percents.
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:
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.
rafter² = rise² + run² = 1.5² + 6² = 2.25 + 36 = 38.25
rafter = √38.25 = 6.18 m
pitch = rise / run = 1.5 / 6 = 25%
angle = arctan(pitch) = arctan(0.25) = 14°
x = pitch * 12 = 0.25 * 12 = 3