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Terry Collins
Sustainability consultant
Asked a question last year

What is a Floor Area Ratio (FAR)?

What is a Floor Area Ratio (FAR)?

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Ross Kim
Geotechnical engineer

Floor area is a ratio of two area

Floor area = total floor area of all floor of building/total building plot area (land area)

FAR is restricted by local jurisdiction authority

If FAR is more that mean we can build more floor area or more story for perticular land.

Lets see one example

Land plot area is 1600 sq ft

We have 5 story building & each story have 1000 sq ft floor area

FAR = 1000X5 / 1600 = 3.125

Our FAR for this building is 3.125

Floor Area Ratio(FAR) is the ratio of buildings total area to the area of land upon which it is constructed.

FAR is also known as Floor Space Index.

FAR = Total area of all the floors of building/area of a plot

Jayden Adams
Construction Assistant

We all are giving priority to some important factor while buying and selling any item, E.g., Mileage for car, carat for gold, similarly the most important issue when we are buying or selling a house or property is the area.

Whether the building is residential or non-residential, area is important for all types of buildings. If there is a transaction of Agricultural land, it is preferably in hectare or acre, etc. However, when it comes to built property (NA plot), it can be in square feet or square meters, and for NA plot (Non-Agricultural) plot FAI or FSI is an important factor, it may strictly affecting on the valuation of this plot,

FLOOR AREA RATIO (FAI) It is also known as FSI. As a definition, it is the ratio of a building's total floor area (gross floor area) to the size of the piece of land upon which it is going to built. As a formula: FAR = (total covered area on all floors of all buildings on a certain plot, gross floor area) / (area of the plot).

For better understanding, please refer photo attached.

Now here's one example for better understanding. If you have 2000 SqFt plot where you want to construct a home, & the FAI of that is is 1.5, then you have 3000SqFt permissible area for construction. You can use it as per your plan. For example, 1500Sqft for Ground Floor and remaining 1500 for the 1st floor.

Remember one thing FAR, rule, and regulations are introduced by the govt. Authorities. You can find out your zone FSI on your state govt's official website. Generally, different buildings have different FSI regardless of the location. And also we can buy extra FAI from respected authorities by paying fees, it is known as Premium FAI. Thank You

Floor area ratio is defined as the ratio of the total floor area to the area of the land at where it is built.

We can write formula as,

FAR = gross floor area/total area of the plot

Ricardo Kuhn
Construction Foreman

Floor area ratio (FAR) is the ratio of a building's total floor area (gross floor area) to the size of the piece of land upon which it is built. It is often used as one of the regulations in city planning along with the building-to-land ratio. The terms can also refer to limits imposed on such a ratio through zoning. As a formula, FAR = gross floor area/area of the plot

What does FLOOR AREA RATIO mean: 

FAR is a technical term used in Urban Planning that determines the total built-up space of the building on a plot of land. Generally, the FAR of the City or the Area is fixed by the government, based on various parameters like infrastructure, population or population growth. These you will understand once you are going through this issue. So by Definition FLOOR AREA RATIO (FAR) is the ratio of BUILDINGS TOTAL COVERED AREA to THE SIZE OF THE PLOT on which it is built. 

BUILDINGS TOTAL COVERED AREA is the Gross Floor Area.

 Formula for FAR FAR = TOTAL COVERED AREA (ALL FLOORS)/ AREA OF PLOT. 

For e.f. If there are 4 Floors and each Floor is of 5000 Sq feet,

 then the Total Covered Area of all the Floors is 20000 Sq Feet and the size of the plot is 10000 Sq Feet,

 then FAR = 20000/10000 = 2. In some areas it is mentioned as % i,e, 200% or somewhere it is mentioned simply 200. 

So if it is 200 then it means the FAR of the City or Area is 2, meaning one is authorized to build up the covered area 2 times to that of the plot area. 

But Generally FAR is fixed by the government, for particular City or Area and the FAR can be used to calculate the Total Covered Area that is built on a plot of land. 

NOTE: There is one more term FLOOR SPACE INDEX i.e. FSI. The meaning of FAR and FSI is the same. There is a difference of only denoting these two. FAR is always mentioned in percentage. 

For e.g. the FAR of any City / Area is 200% then the FSI of the same City / Area will be denoted as 2.0. Let us understand with the help of an illustration as in the image below: For e.g. the total Plot Area is 10000 Sq feet 

CASE 1: If FAR of a place is 0.5, then the total area to be built up is allowed only 5000 sq feet. OPTION A: One can construct in 50% of the plot area, only one floor of 5000 sq feet. So FAR = 5000/10000=0.5 

OPTION B : One can construct in 25% 2 Stories of 2500 sq feet of each. So FAR = (2X2500)/10000=5000/10000 = 0.5

CASE 2: If FAR of a place is 1.0, then the total area to be built up is allowed only 10000 sq feet. OPTION A: One can construct in 100% of the plot area, only one floor of 10000 sq feet. So FAR = 10000/10000=1.0 

OPTION B : One can construct in 50% of the plot area ,2 Stories floor of 5000 sq feet. So FAR = (5000 X 2) /10000 = 10000/10000=1.0 OPTION C : One can construct in 25% 4 stories of 2500 sq feet of each. So FAR = (2500 X 4) /10000=10000/10000 = 1.0 

CASE 3: If FAR of a place is 2.0, then the total area to be built up is allowed only 20000 sq feet. OPTION A : One can construct in 100% of the plot area ,2 Stories of 10000 sq feet each. So FAR = (10000 X 2 )/10000 = 20000/10000=2.0 

OPTION B : One can construct in 50% of the plot area ,4 Stories floor of 5000 sq feet. So FAR = (5000 X 4) /10000 = 20000/10000=2.0 

OPTION C : One can construct in 25% 8 stories of 2500 sq feet of each. So FAR = (2500 X 8) /10000=20000/10000 = 1.0 

So if you know the FAR, you can calculate the total covered area that can be built on the plot. How much open area you have to leave or how much area can be built up depends on the zoning and planning regulations also. For e.g. how much area to be left for:

Setback. Parking Ground Coverage or Maximum Ground Coverage. Height Restrictions

FACTORS URBAN DEVELOPMENT AUTHORITY CONSIDER WHILE DECIDING FAR:

The current population of the City / Area: When the population of the City / Area is high, the FAR is also high, it means the government is intending for Vertical Development as compared to the spread-out development, Population Growth: If the population growth rate is high, then also the FAR of the City / Area is high Infrastructure: Infrastructure also plays a key role while deciding the FAR of the City / Area. If Infrastructure is low then FAR will be kept low otherwise there will be pressure on infrastructural facilities viz, water, power supply, transport etc. If Infrastructure of the City / Area is already high and developed by the government relative to population density, then FAR can be kept at a higher level by the Authorities.

Note: If in the City / Area, the infrastructure is low but the population is growing at a faster rate, then the government has to increase the infrastructure and FAR has to be kept higher to accommodate the high growing population. So when FAR increases the Population Density of the City / Area increases. IMPACT OF HIGH FAR:

Higher Population Density Stress on Infrastructure Better Profitability for Developers High Land Value Better Walkability

IMPACT OF LOW FAR:

  • Lower Population Density. 
  • Better Per Capita Infrastructure Reduced Profitability for the Developers. 
  • Low Land Prices.
  •  Long Travel Distances