First, measure the width and height of all surfaces you want to cover with film.
Then, based on the available film width, you can plan how many pieces you need and what film length is required.
Be sure to allow some extra for trimming, edges, and possible waste.
For wood, stone, or patterned designs, also pay attention to the direction of the pattern. If several fronts are placed side by side, a little extra film may be helpful to ensure the décor creates a harmonious overall look.
A small sketch with all required surfaces and measurements will help with planning.