Floor Space Index (FSI) and Floor Area Ratio (FAR)

In this article we will discuss about basic and foremost important concept of Zoning and Planning Regulation that is FSI and FAR.

FSI and FAR is an outcome or ratio of building’s total floor area to the size of the land upon which the building is built. And the floor area ratio can be calculated by dividing the total or gross, floor area of the building by the gross area of the lot. We consider FSI and FAR as synonyms terms and in common parlance we take them as same but, FSI is index while later is ratio; for example if FAR is 1.5 than FSI will be 150%.

FSI means the ratio between the area of a covered floor (Built up Area) to the area of that plot (land) on which a building stands.This numeric value indicates the total amount of area (on all floors) you can build upon a plot.

Source : Google

Origin of concept FSI in India:

FSI (Floor Space Index) rules and regulations were introduced in Mumbai in 1964.
Rule 2(3)(42) of the Development Control Regulations for Greater Bombay, 1991 (DCR) defines Floor Space Index (FSI) as the quotient of the ratio of the combined gross floor area of all floors, excepting areas specifically exempted under these regulations, to the total area of the plot:

FSI = Total covered area on all the floors / Plot area

 FSI is the ratio between the built-up area allowed and plot area available (FSI = Total Covered Area on Floor ÷ Plot Area). If FSI is 1 then on a plot of 100 square meters, one can build 100 square meters of built-up area and with setbacks (area of the land between the front building line and street alignment) and open spaces, the building can be higher than one floor. In uncomplicated language, the higher the FSI, the higher is the built-up area. Mumbai city is divided in two parts: (i) Island city and, (ii) Suburbs. According to the provisions of the DCR and other authorities the island city has an FAR ranging between 3 - 5. The State Government has drafted a policy for applicable FSI to the state of Maharashtra. It varies from city to city and municipality to municipality depending upon the population density.

What is FSI with respect to the construction?

To explain Floor Space Index (FSI), we will take an example:

Assume that you have a land of 2000 sq. ft and you want to construct a building on that land. Firstly, you need to know what type of building it is and what are you planning to construct.

For the sake of our example, we will rely on the following three types of the buildings:
  • Ordinary Building – Up to 2 floors less than 4 flats/dwelling units,
  • Special Building – more than 2 floors not exceeding 4 floors,
  • Multi-storied Building – Exceeding 4 floors
There are other types of buildings also namely Industrial Building, Group housing etc. 

Based on your building type, find out your zone FSI, which you can find on the State Government’s official website. Generally, different buildings have different FSI regardless of the location. For the same location, FSI can vary for ordinary building and special buildings.
Let’s say, your zone FSI is 1.5 for special buildings. Now you can build (2000 x 1.5) 3000 sq.ft covered area on your land. It can be either 2 floors of 1500 sq.ft or 3 floors of 1000 sq.ft without affecting other municipal rules.

There some other zoning and planning regulation, which we will discuss in other articles later:
  • Minimum plot extent area
  • Front, back, side and rear setback
  • OSR and parking space
  • Height Restrictions.

Why is there a need for FSI

Previously, building activities past happened without any control. Therefore, considering the need for ventilation and safety, governments thought it prudent to set limits on construction by way of FSI norms. This limit plays a crucial role in controlling the expansions of buildings, especially in metros. Higher FSI for an area indicates greater building volume. Therefore, among all the regulations in development planning, FSI is the most crucial. Since many people migrate to cities for job opportunities, FSI limits help regulate vertical building growth and living conditions, while accommodating the burgeoning population.
While determining FSI, apart from the carrying capacity of land, various other related aspects such as adequacy of water supply, sewerage system, solid waste disposal and road capacity are taken into consideration. This is why FSI varies with each state and each region within a state. FSI varies with the type of building as well.

Mainly following factor is responsible for deciding FSI / FAR:
  • Current population of City/Area
  • Population Growth
  • Infrastructure
Premium FSI

The fees paid to the government for this type of construction is known as FSI fees. Now, if a developer wants to build over and above the FSI limit, the authorities sometimes give permission to do so by paying an additional fee. This is termed as premium FSI. A developer can utilise the area (over and above the FSI limit) for providing additional amenities such as flower bed, gardens, balcony and private terraces.

Regardless of zone, location and building type, there are some allowable deviations such as a Premium FSI. If you need to extend the allowable Floor Space Index (FSI), you have to pay a premium fee to the Government.


  1. A very Articulated Article, in a very lucid language, anyone who is looking for the basics of FSI/FAR/Premium FSI , this article will suffice there utility. Very well written.

  2. Explanation provided about FSI concept is very helpful to understand. Easy language, real time example and supporting diagram make this blog very interactive. I really look forward to such insightful and informative blogs in future. Eager to read and learn what is next now!!


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