What is FSI (Floor Space Index) or FAR – Complete Information

We all come across FSI or Floor Space Index but many of us hardly know what it means. FSI is also referred to as FAR that is Floor Area Ratio. Read this for full post to understand the basic concept of FSI or FAR.

Construction industry has always been demanding hike in FSI, so that they can construct higher building and earn more profits. Higher value of FSI or Floor Area Ratio is also indicator of development and progress of that particular area.

FSI in simple terms is the permissible area available to construct house or building in your plot. Total plot area can not be used to construct, thus suitable value of land should be left in order to have air circulation and other important functions for any building.

What is Floor Space Index

Floor Space Index is given by the ratio of total constructed area to the total land area on which construction is to be done. Note that total constructed area exclude certain area like exterior spaces, parking area, patios, balconies, etc.

You can find the list of area included and excluded in FSI from the list given below.

FSI in mathematical form is given by,

FSI = Total built up Area/ Total Plot Area

Built Up Area in FSI

Total built up are include only usable space in a building excluding certain area.

The list of area included in FSI and excluded are given below.

Sr.
No.
Area included in FSIArea excluded in FSI
1.Carpet Area or Tenant AreaExterior Area
2.StaircaseParking Area
3.Basement, Meeting RoomBalconies
4.Storage Room, Laundary or Rest RoomsGarden and Patios
5.Mechanical Equipment AreaOutdoor Courts
FSI (Floor Space Index)
FSI (Floor Space Index)

Other Terminology Used for FSI

Floor Space Index as said earlier is commonly referred to as Floor Area Ratio (FAR) but there are many other names which are interchangeably used. FSI is also referred to as Floor Space Ratio (As it is the ratio of spaces), Gross Plot Area (GPA) Site Ratio or Plot Ratio.

Scroll down or click to Read the list of countries and commonly used term for FSI.

Difference between FSI or FAR

Even though FSI and FAR are interchangeably used but they are not the same. The most prominent difference is the value of both of them.

From the naming convention it is clear that FSI is an Index value, whereas FAR is a ratio. As we know that index is represented as percentage of base figure. While ratio is division of two numbers.

For example,

Assume Plot area of 100 m2, and permissible area to be constructed is 150 m2.

Therefore FAR = Gross floor area/Total plot area

FAR = 150/100 = 1.5

FSI will be represented as percentage and will be equal to 150%

Thus FSI = 150%

Why is FSI important

FSI is used to indicate the density of construction in a given region. Higher the value of FSI in a region, indicates a denser construction.

Local municipal government appropriate authority regulate the value of FSI based on various factors like population density, open space availability, environmental impact and resiliency to a natural calamity.

After carefully analysing all factors local government allot FSI accordingly. Based on the FSI the builder construct building abiding the building bye laws.

FAR or FSI practical example

Suppose in a particular area based on density of the population and other factors a municipality gives FSI of 2. That means a developer or builder can construct area of two times that of the land area.

Suppose that developer want to develop a property on a land of 100 m2.

As FSI is 2, the total usable floor area that can be constructed on a plot of 100 m2 is

Total usable floor area = 100 x 2 = 200 m2

The builder can construct 200 m2 of floor area on a land of 100 m2 by constructing multiple floor on building.

One thing to note here is that this 200 m2 of floor area is only usable are excluding parking, balconies, garden and other setback areas.

Suppose that 50m2 of area is used in parking and other areas that are excluded from the window of FSI.

That means total area builder will construct can be 250 m2 but only 200 m2 of area can be used by inhabitants.

The builder can construct building on 50 m2 of plot area and leave 50 m2 of plot for ventilation an air circulation. Four storey building of 50 m2 area constructed on each floor will amount to 200 m2 of floor area excluding certain area that are not accounted in FSI.

Floor area on each floor = 50 m2

4 storey building, Total area = 50 x 4 =200 m2

Thus if FSI changes to 3, the built up area will be 100 X 3 = 300 m2.

Purpose of Floor Space Index

Every government want to have a control on the population of an area so that it can effectively provide basic amenities to its citizens. FSI is one of the tool to divide the land into appropriate zones to restrict density.

Local municipality gives FSI accordingly to control the population of a particular zone. If local government want to decrease density of a zone it can curtail or decrease the FSI so that less construction is done on a given plot.

For example if FSI of a area is 0.5 then only half of the plot area can be constructed. Hence if 10,000 sqft of plot is to be constructed then only half of it can be constructed, which comes to be 5,000 sqft.

Accordingly architects can plan to construct single floor of 5000 sqft or 5 storey building of 1,000 sqft each. But in no case it can surpass the value of permissible area of 5,000 sqft.

Impact of Floor Space Index (FSI) on Property prices

As said earlier higher FSI indicates development and growth of a region. Thus FSI indices influence the price of a property.

Higher FSI means a developer can build greater flats and thus sold more unit of houses that will finally sold for greater profits. If FSI values increases in a region then the Property prices also increase considerably. Read more about Floor Area Ratio from here.

How is FSI referred to in other countries

Although the basic function of FSI is to measure the density of construction in a particular area. But different countries are using different terms which you can find in the below table.

Sr.
No.
TerminologyCountries
1FSI (Floor Space Index)India,
2FAR (Floor Area Ratio)United States, Canada, India
3FSR (Floor Space Ratio)Australia, Canada, US
4Plot Ratio or
Site Ratio
United Kingdom, Hong Kong
5GPR (Gross Plot Area)Singapore

What is Premium FSI

Floor space index of a building can be extended more then the permissible FSI under certain conditions. But to extend the FSI you need to pay premium fee to the government in order to avail extra FSI.

Extra FSI is allowed only if the adjoining road that leads to the building or property is wider then 30 feet. If your access road is wider then 30 ft then by paying premium fee to the government you are allowed to construct a larger floor area then that is permissible.

Sr. No.Width of RoadPremium FSI
130ft – 40ft Road20%
240ft – 60ft Road30%
3Wider then 60ft Road40%

Frequently Asked Questions (FAQ’s)

Some of the most frequently asked questions about Floor Space Index are given below:

How to calculate floor space ratio?

Floor space ratio is calculated by gross floor area by the total area of the plot.
FSI = Gross Floor Area/Total Plot Area

What is floor space index

Floor Space Index is the ratio of total floor area of a building to the total area of the plot on which it is built.

Floor Space Index value ranges from?

Floor space index depends upon the locality of the plot size of access road, Bye laws of the local government and many other factors.
Approximate value of floor space index ranges from 0.5 to 5.

What is the difference between FAR and FSI?

Floor Area Ratio and Floor Space Index are primarily same but the main difference between floor area ratio and floor space index is that one is a ratio and other is represented as percentage.

Can we get excess FSI greater then the permissible FSI?

FSI greater then permissible FSI is allowed but in certain condition and differ from place to place.
Premium FSI can also be bought, which is greater then the allowed FSI by paying premium fee to government. But it is allowed if the adjoining road is of certain width, which is given below:
20% premium FSI for 30ft to 40ft wide road
30% premium FSI for 40ft to 60ft wide road
40% premium FSI for more then 60ft wider road

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