Use the VELUX Roof Pitch app to measure the pitch of your roof and thereby your choice of roof window.
The height and placing of the roof window have to be adjusted according to the pitch of the roof.

The lower the roof pitch the longer the roof window. VELUX recommends that the top of the roof window is installed app. 200 cm above the floor.

Place your phone directly on the roof to see the pitch or use the build-in camera mode to find the pitch directly.

Website: www.velux.com