Loading factor essentially creates a relationship between the super built-up area and the carpet area. It is the factor which when added with 1 and then multiplied by the carpet area gives the super built-up area.
The correct formula for calculating loading factor is: Super built-up area = Carpet area (1+ loading factor)
Carpet area is the actual area where you can put carpet on. The built up area is the area including carpet area as well as the area of walls and ducts. It is generally 10% more than the Carpet area. Where as the Super built up area is the area including Carpet area and areas of common spaces such as stairs and lifts. It is generally around 25% more than the built up area.