Steeper Pitch: Longer Window.
A roof window should always be placed in the correct height and have the correct size to suit your specific needs.
Choosing the correct window size has to do with the roof pitch on your house. If you have a low roof pitch you need a larger roof window height to have the same view as in a house with a steeper roof pitch. A general rule is therefore that "the lower the pitch of the roof, the higher the roof window".
In addition to the size of the roof window you should also consider in which height to install the roof window. It is important that most occupants in the house have a clear view out the window.
There is no one single "correct" window size or window placement. The window should always be placed for the convenience and functionality of the users, and this can vary according to the conditions.
For the same view, a shallow pitch roof requires a taller window than a roof with a steeper pitch.