Roof Calculator | Roof Interior Space | Roof Pitch

Roof Pitch Calculator

Calculates the roof pitch in degrees and in percent from length and height. Length is the horizontal line from the roof slope to a point, length is the distance from there up to the slope again. Please enter two values with the same units (like inches or centimeters). The pitch will be calculated.

How to determine the roof pitch: measure length and height, the inclination angle is the angle to the left, here about 22 degrees.

Length (l):
Height (h):
Inclination angle (degrees):
Inclination in percent:

An example that fits the picture above: if you measure a length of 93 centimeters and a height of 37 centimeters, then the angle of inclination of the roof is 21.7 degrees, which corresponds to almost 40 percent.

For a straight flat roof, the measured height would be zero for any length, so the angle of inclination would also be 0 degrees and the percentage slope would also be 0. In Germany, according to building regulations, a roof is considered flat up to a slope of 10 degrees, whereas in Austria, it is only up to 5 degrees. Other countries may have different regulations and designations.
For larger angles, the term "pitched roof" is used. According to DIN 1055, "Influences on Load-Bearing Structures," this starts at a slope of seven degrees. Up to a range of 22 to 30 degrees, a roof is referred to as a gently pitched roof, and above that, it is referred to as a pitched roof. The roof in the example above is therefore gently pitched, just barely, depending on the definition.
The steeper a roof, the higher it is for the same floor area. With tall roofs, more material is required to gain the same amount of space, or less space is available below the slopes for the same amount of material. However, pitched roofs are considered more durable and less maintenance-intensive. The most sensible roof shape depends on several factors, including location. Expert advice is recommended. A local building plan may also dictate the roof shape.

Last updated on 06/26/2025. Author: Jürgen Kummer

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See also Staircase Calculator, Calculate the Slope