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Importance and Calculation of Floor Space Index(FSI) or Floor Area Ratio(FAR)

What is Floor Space Index(FSI)?

The floor space index is calculated by dividing the total size of the building’s floors by the total area of the site on which those floors are located. The built-up area is another name for the area that all the floors cover. Moreover, in some areas, the floor space index (FSI) is also known as the floor area ratio (FAR).

In general, it is a ratio that aids in determining how much construction must be done on a plot of ground.

The facilities, building type, and zone category of the city are just a few of the variables that affect the floor space index’s value. The total number of structures that can be built on a certain plot will vary depending on a number of factors, including the plot’s size, location, and intended use. Developers must adhere to the floor space index set by the governing body. The floor space index, also known as the floor area ratio, also incorporates a number of other components that have been established by various State and municipal governments.

Currently, various governing entities, such as Municipal Corporations, Municipal Councils, and other agencies, have varying standards for setting the maximum FSI for a given region.

The gross floor area is a further concept associated with the floor space index/floor area ratio (GFA). The GFA is the total square footage of the building, excluding elements like the parking lot, balcony, driveway, walkways, etc.

Importance of Floor Space Index(FSI)

FSI/FAR is essential for regulating urban density. It is essentially necessary because there is a finite amount of available space and capacity in every metropolis. Any use that exceeds this limit puts an undesirable strain on the city. Unauthorized and unlawful constructions will emerge in the absence of FAR/FSI rules.

Building density is directly regulated by FSI/Far value inside a land grant. More building volume and a dense or highly urbanised area are both indicated by higher ratios. To provide the best possible quality of life in the area, local municipal corporations decide on the FAR value.

Admissible FSI/FAR value is determined by:

  • The plot’s size
  •  Population’s density
  • Accessibility to open spaces, power, water, and sewer lines
  • Type of structure (residential, commercial, institutional, etc.)
  • The project’s environmental impact and
  • A state of preparedness in case of a natural calamity.

Calculation of Floor Space Index(FSI)

The gross floor area (total built-up area) of a plot of land and the maximum number of stories a building can have are determined using FSI.

Total Built Up Area= Total plot area X FSI

No. of floors= Total  Built-Up Area/ Maximum Plot Coverage

For instance,

You are assigned a floor space index of 1.5 for a specific plot area of 2000 square feet. And you have plans to erect a unique structure there. Then

Total Build Up Area equals 2000 x 1.5 or 3000 square feet.

Without influencing other municipal regulations, it may be either 2 levels of 1500 square feet or 3 levels of 1000 square feet.

The same applies if your property is 10,000 square feet and your FSI is 2. Let’s say you plan to build a multistory structure there. Then, you can erect covered structures of up to 10,000 x 2 = 20000 square feet.

Advantages of Floor Space Index(FSI)

The major advantages of Floor Space Index(FSI) are  

  • It demolishes illegal structures.
  • It guarantees the efficient utilisation of city resources.
  • It keeps the proportion of open space to built-up area constant.
  • It keeps a city’s skyline intact.
  • It assists government officials in promoting steady and deliberate growth.

What is Premium Floor Space Index?

Paying a charge to the government in order to increase the permitted FSI is known as premium FSI. It offers additional versatility. However, the neighbouring road of the land must be at least 30 feet away in order to receive premium FSI.

The following premium floor space index might be used in addition while taking into account the various main road width circumstances:

  • The builder can obtain a 20% extra floor space index if the road width is between 30 and 40 feet.
  • The builder is eligible for 30% extra FSI if the road width is between 40 and 60 feet.
  • The builder may use 40% extra FSI if the road width is greater than 60 feet.
  • With a 20% greater floor space index, construction can be allowed to exceed the actual permitted amount by 20%.

Components of Floor Space Index(FSI)

Basic and Fungible floor space index are the two parts of FSI that can be used in building construction. The maximum FSI that can be applied to a plot is the sum of these two elements.

  1. Basic FSI: This is the FSI that is offered without charge.
  2. Fungible FSI: The local authorities must be contacted in order to purchase this component of the FSI. There is some FSI available for purchase in addition to the fundamental FSI. This must be purchased by paying a premium based on the region’s Ready Reckoner or circle tariffs, or the sum determined by the appropriate governing authority.

Floor Space Index of India’s Largest Cities

City  Governing Body FSI for Residential Projects  FSI for Non-Residential projects
Minimum  Maximum Minimum  Maximum
Mumbai  Municipal Corporation of Greater Mumbai 1 4 1 5
Kolkata Kolkata Municipal Corporation 1.25 3 2 3
Gurgaon Haryana Urban Development Authority 1 1.75 1 2.5
Bengaluru Bruhat Bengaluru Mahanagara Palike 1.75 3.25 1.5 3.25
Chennai Chennai Metropolitan

Development Authority

2 4.87 0.75 1.5
Noida Noida Authority 2.75 3 1 4


The density of the piece of land increases with the floor space index/floor area ratio. However, the floor space index/floor area ratio is not the only factor affecting the property’s price. Additionally, if the major road is at least 30 feet wide and adjacent to the property, the builder can take advantage of a premium floor space index/floor area ratio. In ideal circumstances, the conventional floor space index/floor area ratio in most places does not exceed 2.5.

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