Floor Space Index, also known as Floor Area Ratio, is the total ratio of the cumulative area of all the floors from all the buildings to the size of the land on which such buildings are made. In other words, FSI is the ratio between the area of a covered floor, i.e. the built-up area or the plot size on which the construction takes place, to the area of that plot on which a building stands, i.e. the coverage area permissible. It is a directive followed in the development control norms of many Indian cities to control their densification and expansion. For instance, when we say the FSI in a particular location is 1.5, it means that if there is a 10,000 sq. ft. the plot, the total floor area cannot exceed 15,000 sq.ft. The FSI value may vary from place to place depends upon the location, municipality, government regulations, etc.
The formula for calculating FSI is:
To understand the Floor Space Index (FSI) better, have a look at this:
Presume, you have a land of 4000 sq.ft and you are desired to construct a building on your land.
The foremost thing that you need to figure out is what type of building you are planning to construct?
(There might be other types of buildings but for the sake of this example, we are sticking to these types)
Note: Considering your building type, find out your zone FSI on your state government’s official website.
Let’s assume, your zone, in particular, having FSI of 1.5 for special buildings. Now you can build (4000*1.5 ) 6000 Sq.ft covered area on your land. It can be either 4 floors of 1500 sq.ft or 6 floors of 1000 sq.ft without affecting other civic rules.
Note: You are also obliged to follow other municipal or civic rules such as Open Space Reservation and parking space, Minimum plot area etc.
Purpose of FSI:
The main purpose of FSI is to limit the building density, thereby also limiting the number of people that a building can hold. Consequently, it also has a major impact on the value of the plot. Higher allowable FSI leads to higher plot value and vice-versa.