Carpet area is the area within the walls of an apartment that is for the exclusive use of the buyer. While computing the carpet area, the terrace and balconies are usually considered as half the actual area.
Built-up area includes the carpet area and thickness of external walls, internal walls and columns. It is typically 10-20% more than the carpet area and is also sometimes known as the plinth area.
Super built-up area includes common amenities, such as the area of lift shafts, lobby, and corridor, proportionately divided among all flats. The common usable areas, such as a swimming pool, garden and club-house, may also be included in it.
Per square foot rate quoted by the developer is typically applied on the super built-up area to determine the value of the flat. This is the reason super built-up area is also sometimes referred to as the saleable area.
Floor Space Index (FSI) is the ratio between the total built-up area and plot area available allowed by the government for a particular locality. Premium FSI refers to permission obtained to build extra floor space by paying a premium.
Source: Economics times