What Is Floor Space Index (FSI) Or Floor Area Ratio (FAR)?

Floor Space Index (FSI) or Floor Area Ratio (FAR) are two significant terms used in the field of real estate. In this article, we will discuss what is FSI or FAR and how to calculate it.

What Is Floor Space Index (FSI) / Floor Area Ratio (FAR)?

Floor space index (FSI) or floor area ratio (FAR) is the ratio of a building’s total constructed floor area (built-up area) and plot area (land area). In simple words, it is the maximum permissible area that can be used to construct buildings/structures in a plot of land.

Floor Space Index is regulated by the local municipal or development authorities of the respective State government. Therefore, It varies from one city or even locality to another. FSI norms are normally based on the National Building Code. It is sometimes also termed as floor space ratio (FSR).

floor space index (FSI) Premium FSI, Floor area ratio

Why Floor Space Index (FSI) / Floor Area Ratio (FAR) Is Important?

FSI/FAR plays a vital role in controlling urban density. It is essentially required because every city has limited space and limited capacity that can be used safely. Any use exceeding this limit creates unwanted pressure on a city. In the absence of FAR/FSI rules, unauthorized and illegal constructions will increase.

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FSI/Far value directly limits the number of buildings within a plot or land. A higher ratio indicates greater building volume, a dense or highly urbanized area. The FAR value is determined by local municipal corporations, to ensure the best possible living in that area.

Permissible FSI/FAR value depends on:

  • Size of the plot
  • The density of the population,
  • Availability of open spaces,
  • Availability of power, water, sewer lines
  • Type of building (residential, commercial, institutional, etc.)
  • Environmental impact of the project and
  • Preparedness in the eventuality of a natural disaster.

FSI/ FAR value may be changed from time to time depending on the growth of each city. It should also be noted that buildings with different numbers of stories may have equal FAR values. Although the permissible FSI ratio or FAR value differs from place to place, the value generally does not exceed 2.5.

How To Calculate Floor Space Index (FSI) / Floor Area Ratio (FAR)

FSI is used to calculate the gross floor area (total built-up area) for a plot/land and also to calculate the number of floors the building can have.

Formula to calculate the total built-up area

Total Built Up Area = Total plot area X FSI

To calculate the number of floors allowed

No. of Floors. = Total Built-Up Area / Max. Plot Coverage

(If you need to increase the no. of floors, then you will need to reduce the plot coverage from its maximum permissible coverage)

You can find the Floor Space Index on your state govt’s official website. But, First thing you need to know is what type of building you are planning to construct. There are different types of buildings

  • Ordinary Buildings – Up to 2 floors less than 4 flats/dwelling units,
  • Special Buildings – More than 2 floors But not exceeding 4 floors,
  • Multi-storeyed Buildings – More than 4 floors

There are other types of buildings that also exist such as industrial buildings, institutional buildings, etc.

For example,

You have a particular plot area of 2000 square feet where FSI or floor space index 1.5 is allotted. And you are planning to build a special building there. Then

Total Built Up Area = 2000 x 1.5 = 3000 sq.ft

It can be either 2 floors of 1500 sq. ft or 3 floors of 1000 sq. ft without affecting other municipal rules.

Similarly, if you have a land of 10,000 sq ft and the FSI is 2. Suppose you are going to construct a multi-storeyed building there. Then, you can build up to 10000 x 2 = 20000 sq ft of covered structure.

Then no. of floors would be 5 floors of 2000 sq. ft or 10 floors of 1000 sq. ft etc.


You must follow some other municipal rules such as,

  • Minimum plot extent area,
  • Front, back, side, and rear setback,
  • OSR and parking space.

Advantages Of FSI/FAR

Floor space index/floor area ratio may be considered as a restriction for construction but it has several benefits.

  • It maintains the ratio of free space to built space.
  • It maintains the skyline of a city.
  • It helps government authorities to foster stable and planned growth.
  • It eliminates unauthorized constructions.
  • It ensures the proper use of resources in the city.

What Is Premium FSI?

Premium FSI is a fee paid to the government to extend the permissible FSI. It allows more flexibility. But to avail premium FSI, the adjacent road of the land must be at least 30 feet.

Criteria For Premium FSI:

Road width Premium FSI
30-40 ft20%
40-60 ft30%
Over 60 ft40%

For Example, If you have 1000 Sq.ft of Land located near 35 feet road, then you will be able to build 20% more than the allowable Floor space index by paying the premium fee.

Built-up area = Land area x Normal FSI x Premium FSI in percentage


1. What is the difference between FAR and FSI?

The only difference between FSI and FAR is that the first is an index while the latter is a ratio. Index numbers are values stated as a percentage. Hence a FAR of 2.5 is expressed as FSI of 250%.

2. What is included in gross floor area?

Bedrooms, common areas, lobbies, basement, staircase, mechanical equipment areas, laundry, storage rooms, restrooms, and atriums are included in gross floor area.

3. What is not included in gross floor area?

Exterior spaces, balconies, parking, patios, walkways, and driveways that are covered, attics, and outdoor sports courts, are not included in the gross floor area.

4. Is balcony included in FSI (Floor Space Index)?

No, as stated above balconies will not be included in the gross floor area.

5. Is the staircase included in the FAR?

Yes, if the staircase is inside the building.

Also Read

How To Calculate Land Area/Plot Area?

What Is Built-up Area, Carpet Area, & Setback Area

How To Calulate Soil/Sand For Plot Filling

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