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Calculate roof pitch yourself - online tools

  • Necessity of calculation
  • Roof pitch - online tools
  • Two dimensions for the calculation
  • Careful, confusing calculation
  • From angle to percentage slope

The roof pitch can be calculated with online tools, but you can find amazing. We show the online tools for calculating roof pitch and their traps; and the right formula to really calculate the roof pitch yourself.

The roof pitch you have z. B. for the planning of a photovoltaic system know exactly. More precisely than many a half-ruined plan of an old house gives, every inaccuracy costs in doubt your money. Below you will find out how you can calculate the inclination of the roof yourself with the help of online tools and how you can control these calculations yourself.

Necessity of calculation

As the owner of a house, you are already familiar with the roof pitch of your house. If an individual design was made by yourself, you will have talked to the architect about the pitch of the roof. In the prefabricated house, you were dealing with a given roof pitch, which you were informed about in the planning documents.

If you bought an old house, it might look different. There may be plans, they are not always complete when the roof was redone, the roofer had a look and "fits" said - and at the self-built garden shed, no one was interested in the roof pitch, downhill, so that rain expires.

If old house and garden shed are now to be equipped with solar modules, the roof pitch is interesting. It plays a role in the optimal installation of the solar modules, so it decides about your "solar yield". Even before assembling many roof tiles, the exact roof pitch must be determined for the calculation of a new snow guard (sufficient for which snow pressure) as well.

Roof pitch - online tools

Several pages offer the calculation of the roof pitch:

  • Photovoltaiksolarstrom.de - roof pitch
  • Horst Addix - determine roof pitch
  • hbw-handel.de - Roof pitch

However, you should not blindly trust the pages, as they sometimes get different values. It is recommended to carry out the calculation yourself.

Simply enter the measured values ​​a and b and the result is, roof pitch ß in degrees.

Further names for a and b:

  • Horizontal a; Vertical b
  • Length a; Height b
  • Horizontal a; Vertical b

If you would like to discover the inclination of a flat roof, you can easily read it on the page www.dachplattenprofi.de/Glossar/Dachneigung in a table.

Of course, there is also an app for iPhone and iPad to determine the roof pitch. Despite its name "slate tools", this app should also measure the slopes of other roofs. Above all, the mobile multifunction tool makes it easier to work locally when planning a roofing with slate, because you also get a "slate laying bible" with technical details and access to ten thematically sorted films about slate.

Two dimensions for the calculation

As with all the crucial calculations a human being can make in their lifetime, online calculators are nowadays used to calculate roof pitch for computer calculations. You always need the same metrics to enter these online tools. Often, the distances to be measured on the sides are carefully marked, so you can not go wrong.

Or rather, apparently caring; As shown there, you need a very long ladder and strong men to hold on to when measuring, if this adventure should not end in the hospital.

There are many people, including younger people, who would rather spare that B. because they have fear of heights or not so long ladder. Then a company is commissioned, for. As the roofer, who should measure the same with, but charged extra. This shows that you can use online tools, but you can not let yourself lose weight because it can quickly be expensive. If you know what the measurement is about, you will not have any problems in getting the measurements yourself:

The online tools use the geometric figure of the right-angled triangle to calculate the roof pitch.

Right triangle

A right triangle consists of three sides, two of which are connected by a right angle. The third side is the roof pitch

Correct measurement
The right angle is set in your measurement, a and b must be at right angles to each other.

If you are using an online calculator, please check what labels a and b have there. Sometimes both values ​​are also reversed, in capital letters or have completely different names.

With loft
Measure a certain distance from the floor, this is in our example the distance a with 250cm. For example, mark the dot at 2.50 m with some adhesive tape. From this point you create the vertical, which must run at exactly the right angle. You are welcome to use a metal bracket, as you can (and should) assume that your floor is in balance. They measure vertically up to the roof slope and thus receive the distance b with 300 cm. From these two values, you can now calculate the roof pitch using the online tools.

Calculate roof pitch

Without attic
It is a bit harder to measure the roof pitch from the outside. Either you have a high ladder or you come from a window to the roof. It is not necessary to measure large dimensions. The principle is the same as above.

However you bring a, A, y (length, horizontal, horizontal) and at right angles to b (B, height, vertical, vertical) straight to the pitch of the roof, you get two values ​​from which you have the angle ß and thus can calculate the roof pitch. You also do not need to enter the length and height in centimeters, as most tools require. You can enter the measurements in meters, centimeters or (at the roof of the dollhouse) in millimeters. The only thing that matters when it comes to the relationship between the measures is that it "does not matter" when you stick with one unit.

Careful, confusing calculation

Online tools are helpful, but usually leave you "stupidly dying" until the result of the calculation is transmitted, but less helpful in important calculations. Critical customers want to know how to calculate values ​​that directly affect the chances of success of their investments (as is the case, for example, with the roof pitch for the photovoltaic module); Success-oriented guys always like to take the chance to learn something.


The vendors who provide the online tools know that; So some tools want to shine properly with service and explain the calculation, z. For example, with side-length calculation of a right-angled triangle according to the Pythagorean theorem, from which determination of the sine value and conversion of the sine value into an angle.

Basically, this works: Right-angled triangles with 90 ° angles have a longer side, which is opposite to the right angle, the hypotenuse. The two shorter sides forming the right angle are the catheters. Here you make your right triangle, from the measuring lines (catheters) a and b, the roof slope between the points where a and b hit the roof, is the hypotenuse, on all these distances you can apply the theorem of Pythagoras.

From angle to percentage slope

As a rule, the roof pitch is given as an angle in degrees. If you come across percentages of percentages or want to calculate the percentage slope yourself, online tools also help:

Either as a table, eg. B. at www.nordbleche.de, from which you learn that

  • 1 degree = 1.8 percent
  • 25 degrees = 44.5 percent
  • 45 degrees = 100 percent.

Or as an online conversion tool that lets you convert angles to percentages and vice versa. The angle value is entered at "Degrees, Degrees (°)", the percentage at "Percent slope, Gradient (%)", the tool calculates the equivalent value.

Who wants to know exactly - Wiki also helps here: "When converting an angle in percent helps the following formula, it should be noted that we understand a slope of 45 degrees under a 100% slope": angle in percent: 100 x tan α = x%

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