What is FSI and Its Recent Guidelines: 2023

Table of Contents

What is the Floor Space Index (FSI)?

Floor Space Index (FSI)or Floor Area Ratio (FAR) is the standard metric used in urban buildings to ensure safety and ventilation in the livelihood. The higher the FSI the more crowded and dense the space will be. The lesser the FSI would lead to underutilization of the land and be lack of facilities. In simple terms, you cannot raise a building in your plot. If everyone did so, an area would look congested and there would not be any place for people to accommodate during emergencies like fire accidents.


The FSI is set by the local municipal corporation. The right FSI should be adhered to maintain the legal construction and safety of the proposed building.


What is the FSI Formula?

The standard FSI formula is:

 FSI = Total Floor Area of all Floors / The total plot area

However, the FSI may vary from place to place as per the local municipality’s guidelines.


How to calculate FSI for buildings?

Let us learn how to calculate FSI for buildings.

For example, if the total area of your plot is 3600 sq. ft. including the plinth area of four floors. Let’s say the plinth area of a floor is 900 sq. ft. (900+4= 3600).

The total area of the plot is 2400 sq.ft. so, 3600 sq. ft. /2400 sq. ft. = 1.5. FSI = 1.5.

Difference between Floor Space Index and Floor Area Ratio

FSI and FAR are both terms that pop up often in the real estate field. Although both of them serve the same purpose, it is significant to understand the subtlest differences between them. Not only the builders and promoters, but everyone who is going to build a house should know them to make informed arrangements.

  • FAR and FSI are similar in a way that they both determine the development density of a building to prevent overcrowding.
  • Both of them are crucial elements for infrastructure management.
  • Both impact the property’s value and development feasibility.
  • FSI is calculated in ratios (1.5 and 2.5)
  • FAR is calculated in percentage (Multiplying the FSI by 100)
  • FSI is used in India, whereas FAR is used in countries like The U.S. and other countries.
  • A small example of how FSI is calculated is if the total area of the land is 1000 sq. ft. with an FSI of 2.5, you can build 2500 sq. ft. of floor space on the land.
  • FAR is calculated by multiplying the FSI by 100, thus, FAR = 250%


Following are some Real Estate jargons you should know to understand better:

Plinth area

The plinth area is the covered build-up area. It is usually measured at the floor level of a storey or the basement of the building. It is also called the built-up area or the gross floor area.

Floor area

It usually refers to the horizontal area of a building. There are three types of floor area Gross Floor Area, Net Floor Rea, and Gross Internal Area.

Carpet Area

It is also called the net usable area. It is the actual usable area in the property excluding the walls, balconies, and common areas.

Super built-up area

The super built-up area comprises the carpet area along with the sealable areas such as walls, stairs, and balconies.


Setback is the minimum distance kept from other properties and roads to maintain ventilation, safety, and light. In simple words, it is a buffer space.

Open Space Ratio (OSR)

Open Space Ratio refers to the area that must be kept unused for building parks, gardens, and playgrounds.

Land to Built-up Ratio

The land-to-built-up ratio is the carpet area added with the area covered by walls.

Coverage area

The coverage area is the total built area on all the storeys.

Floor-to-Area Ratio

The floor-to-area ratio is calculated by dividing the floor area of a building by the total area of the land.

Zoning regulation

Zoning regulations refer to the guidelines put forth by the local municipal office on DOs and DON’Ts on a property. It may vary from place to place.


What is the use of FSI?

The Floor Space Index is a pivotal tool in real estate. It acts as a regulator of the development density. It determines the maximum permissible built-up area on a land. It is essential to adhere to the required FSI while building. It is calculated by dividing the total floor area by the total area of the proposed land. It is calculated to maintain safety, and ventilation, and allow ample light to the building otherwise, the place would look dense and there would be no buffer space.

Here are some uses of FSI in real estate:

  • FSI controls over density and maintains orderly expulsion in rural areas.
  • It helps balance growth, giving space for parks, gardens, and playgrounds in the proposed land. Overall, it promotes a healthy environment.
  • It helps builders and promoters make informed decisions on the land.
  • FSI encourages effective land utilization.
  • By restricting density, traffic, and congestion are avoided.

What is the average FSI in India?

FSI in India may vary from city to city and locality to locality. Here are some major cities with their FSI:

●     FSI in Mumbai – 2.5 to 5, depending on the locality and development.

●     FSI in Delhi – 1.2 to 3.6. Higher FSI is allowed for some projects.

●     FSI in Kolkata – 1.5 to 3 depending on the type of building.

●     FSI in Bangalore – Typically 2.4 to 4. Higher FSI is allowed for building are allowed under the Bangalore Development Authorities (BDA)

FSI is comparatively low in smaller cities compared to metropolitan cities. It typically ranges from 0.5 to 2.

What is the current FSI in Chennai?

The current FSI in Chennai is 1.25 for residential buildings and 2.5 for commercial buildings. Regarding residential buildings, it rose from 1.5 to 1.25 lately. The revision in the improvement is aimed at developing the city’s infrastructure and housing options while adhering to the regulations and maintaining open space in residential areas. One of the main purposes of the shift in the ratio is the soaring population and to accommodate them.


An FSI of 1.25 means, the builder can build a house or an apartment 1.25 times the size of the plot.


Chennai FSI rules

Chennai has seen a surge in recent days. With people moving in from places all over the state and to accommodate the bustling population, several guidelines were introduced governing FSI (Floor Space Index). The current FSI in Chennai regarding residential buildings and commercial buildings are:

  • Residential buildings – 1.25
  • Commercial buildings – 2.5

The limits put forth by CMDA (Chennai Metropolitan Development Authority) dictate the maximum number of floors that can be built on any piece of land.


That’s a wrap!

In the case of TLDR, FSI is a standard metric followed by development authorities to maintain orderly development in the proposed space. FSI restricts builders from utilizing the entire plot bought, whereas only a particular part can be used, considering safety, ventilation, allowing light, and avoiding over-density.


Frequently Asked Questions

1.   Who decides FSI?

Answer – At the National level, the Ministry of Housing and Urban Affairs frames the FSI. At the state level, Town and country planning departments frame the FSI, at the local level, the Municipal Corporation or the Local Development Authorities decide the FSI.

2.   What are the benefits of increased FSI?

Answer – An increased FSI will result in the construction of new buildings and increased infrastructure, it will also allow existing buildings to be redeveloped.

3.   What is Premium FSI?

Answer – Builders can avail an additional 50% of FSI if the proposed site is situated adjacent to a road that should at least be 30 feet wide. Buildings that suit the requirement are eligible for the premium FSI.

4.   Why is FSI important?

Answer – FSI is important to maintain orderly development, controlled growth, traffic management, and environmental stability. In a nutshell, FSI aims at creating a conducive environment for us.

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