The floor area ratio calculator assists you in estimating the ratio of the different kinds of areas for your home, such as carpet area, built-up area, super built-up area, and total built-up area. Using this data, you can determine how much room is available for use compared to the builder's claim.

In addition to the areas, parameters like floor space index (FSI) or floor area ratio (FAR), open space ratio (OSR), and loading factor are extensively used by realtors and builders to define and promote a property. Are you confused between built-up area vs carpet area debate? Read on to understand what is carpet area and how to calculate floor area ratio and other important indices.

What is carpet area? What is a built-up area?

The carpet area is defined as the area of the floor that you can cover with a carpet. In other words, it means the total usable area in the house. The carpet area means your personal space or is meant for exclusive usage in the house, i.e., it does not include anything outside the house or any common areas. The equation gives the carpet area formula:

Carpet area = Indoor area - Area of walls

Where the indoor area is the sum of all the rooms in the house. The definition of carpet area is commonly shown on the realtor's portfolio for the apartments and houses for sale.

However, some builders prefer to display built-up areas as a means to show their properties. The definition of the built-up area includes the area covered by walls in the house and carpet area. The built-up area formula is:

Built-up area = Carpet area + Area of walls

The difference between carpet area and built-up area is the inclusion of area covered by the walls. The carpet area is smaller than the built-up area. Usually, the carpet area is about 70% of the built-up area, which can be used as a thumb rule to quickly estimate the given built-up area. Further, as we move out of the house, the following classification of the area is the super built-up area.

What is a super built-up area?

The super built-up area means the inclusion of constructed common area around the entrance of the house. The calculation of the super built area is performed by adding the area covered by stairs, foyers, lift, and lobby to the built-up area calculation. Mathematically that's:

Super built-up area = Built-up area + Common area / Number of units

The term common area is used for the sites accessible by all the residents from different connected houses — for instance, the lobby in front of the lift. Similarly, there are several common areas available such as foyers. In some cases, developers also include stairs, pools and gardens. The common areas are proportionally divided and then used in the calculation for the super built-up area. Alternatively, the super built-up area calculation is also performed using the loading factor.

Super built-up area = (1 + Loading factor) * Carpet area

What is the floor area ratio (FAR)? What is the floor space index (FSI)?

The floor area ratio (FAR) or floor space index (FSI) is defined as the ratio of total built area to the total plot area. Mathematically, the floor area ratio formula is:

FSI = Total built-up area / Total plot area

where total built-up area refers to the sum of all built-up areas.

In addition to this, the open space ratio is used to learn about the amount of open space available on the project. The open space ratio (OSR) is the ratio of the amount of open space available on the project to the total project area. Many buyers look for greenery and access to trees and nature, and the open space ratio is the means to identify the open space on the project.

How to calculate floor area ratio (FAR)?

The following steps will tell you what the house's built-up area and carpet area are, how to calculate the built-up area, super built-up area, and the floor area ratio.

  1. Enter the carpet area for the house.
  2. Fill in the built-up area.
  3. The calculator will return the value of indoor areas, carpet area to built-up area ratio, and total built-up area.
  4. Enter the value of the available common area (this area is proportionally added to calculate super built-up area).
  5. The super built-up area calculation is performed and returned.
  6. Enter the area of open space available on the project.
  7. Enter the total land area over the project is built.
  8. The floor area ratio calculator returns the loading factor, open space ratio, and floor area ratio.

Example: Using the floor area ratio calculator

What is the carpet area of the house if the carpet area to built-up area ratio is 60%? Take built-up area as 1400 sq. ft. Further, estimate the floor area ratio given the project has 100 units, and it spans over a land of 4 acres.

In this example, we'll see how to calculate carpet area from the built-up area. We know the ratio of both areas is 60%. Therefore, to calculate carpet area:

  1. Enter the built-up area as 1400 sq. ft.

  2. Fill in the ratio of both areas as 60%.

  3. The carpet area of the house is:

    Carpet area = Built-up area * 0.6 = 840 sq. ft.

  4. The carpet area and built-up area difference is used to estimate the indoor and wall areas.

  5. Enter the number of units as 100.

  6. Insert the total area of the land as 4 acres (174,240 sq. ft.).

  7. Using the floor space index formula:

    FSI or FAR = Total Built-up area / Total land area = 140,000 sq. ft. / 174,240 sq. ft. = 0.8035

    The meaning of the floor area ratio of 0.8 signifies the amount of constructed area and open spaces. The smaller the floor area ratio, the less total construction on the land and more open space.


What is carpet area of house?

The carpet area is defined as the total usable indoor area that can be covered by a carpet.

Is balcony included in carpet area?

The carpet area means the areas that are indoor and therefore, the balconies are not included in the carpet area.

How to calculate super built-up area?

To calculate the super built-up area:

  1. Find the area of common space accessible to the inhabitants.
  2. Divide it by the number of units.
  3. Add it to the carpet area.

What is the floor space index formula?

The floor space index formula is:

FSI = Total built-up area / Total plot area

Rahul Dhari
Carpet area
Built-up area
Carpet to built-up area ratio
Number of units
Super built-up area
Total built-up area
Indoor area
Indoor area
Walls area
Outdoor area
Common area
Open space area
Total land area
Loading factor (LF)
Open space ratio (OSR)
Floor area ratio (FAR) or floor space index (FSI)
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