Floor Area Ratio (FAR) Calculator
Calculate floor area ratio (FAR), FSI, loading factor, and open space ratio for building projects. Free online FAR calculator for architects and planners.
About This Calculator
The Floor Area Ratio (FAR) Calculator helps architects, builders, real estate professionals, and homebuyers determine the building density of any construction project. FAR, also known as Floor Space Index (FSI) in India, is the most important zoning regulation metric used by municipal authorities worldwide to control building density and urban sprawl.
This calculator computes FAR by dividing the total built-up area (built-up area per unit × number of units) by the total land area. It also calculates the Open Space Ratio (OSR), Loading Factor, Super Built-up Area per unit, and Carpet-to-Built-up ratio. The Area Breakdown chart visualizes how the built-up area is distributed between carpet area, wall area, and common area, while the Land Utilization chart shows how the total land is allocated between built-up area and open space.
Regional Notes
India: FAR regulations are enforced by municipal corporations and development authorities (DDA, MHADA, BBMP, etc.). Typical FAR values range from 1.0 to 3.5 depending on the city and zone. In Mumbai, premium FSI of up to 4.0 may be allowed after paying a premium. RERA mandates disclosure of carpet area calculation in all property agreements.
United States: FAR regulations vary by city and zoning district. For example, New York City has FAR limits ranging from 0.5 in low-density residential zones to 15.0 in high-density commercial districts like Midtown Manhattan. Some cities use Floor Area Ratio (FAR) while others use Lot Coverage as the primary density control.
United Kingdom: The UK does not use FAR as a universal metric. Instead, density is controlled through local planning policies, with typical residential densities of 30-100 dwellings per hectare. However, the concept of plot ratio (similar to FAR) is used in commercial developments and urban planning assessments.
Frequently Asked Questions
What is Floor Area Ratio (FAR)?
Floor Area Ratio (FAR), also known as Floor Space Index (FSI), is the ratio of a building's total built-up area to the size of the plot or land on which it is constructed. It is calculated by dividing the total built-up area of all floors by the total land area. FAR is a critical zoning regulation used by municipal authorities to control building density and urban sprawl.
How is Floor Area Ratio calculated?
Floor Area Ratio is calculated using the formula: FAR = Total Built-up Area / Total Land Area. For example, if a building has 10,000 sq ft of total built-up area on a 5,000 sq ft plot, the FAR is 2.0. A higher FAR indicates denser construction, while a lower FAR means more open space remains.
What is the difference between carpet area and built-up area?
Carpet area is the actual usable floor area within a unit, excluding wall thickness. Built-up area includes carpet area plus the area covered by walls. In typical Indian apartments, the built-up area is approximately 25-30% larger than the carpet area. For example, a 1,200 sq ft built-up area may have a carpet area of around 900-960 sq ft.
What is a loading factor in real estate?
Loading factor is the percentage difference between the super built-up area and the carpet area of a property. It represents the proportionate share of common areas like lobbies, staircases, elevators, and corridors allocated to each unit. A loading factor of 25-35% is common in Indian residential projects, while luxury projects may have higher loading due to larger common amenities.
What is a good Floor Area Ratio value?
FAR values vary by city and zoning regulations. In India, municipal corporations specify maximum FAR limits for different zones: typically 1.0-1.5 for residential low-rise, 2.0-3.0 for residential high-rise, and 1.0-2.5 for commercial areas. In the US, FAR ranges from 0.5 in suburban areas to 10-15 in dense urban cores like Manhattan. In the UK, density is controlled through local planning policies with similar ratio-based restrictions.
What is Open Space Ratio (OSR)?
Open Space Ratio (OSR) is the proportion of open space area to the total plot area. It indicates how much land is left as open space after construction. OSR is calculated as: OSR = Open Space Area / Total Land Area. Most municipal regulations mandate a minimum OSR of 15-25% depending on the zone and city.
What is super built-up area?
Super built-up area is the built-up area plus the proportionate share of common areas such as lobbies, staircases, elevator shafts, clubhouse, and other amenities shared by all residents. It is calculated as: Super Built-up Area = Built-up Area + (Common Area / Number of Units). Developers often use super built-up area for pricing, which can be significantly higher than the actual carpet area.
How can I verify the FAR claimed by my builder?
To verify the FAR claimed by your builder, obtain the sanctioned building plan from the local municipal authority. Check the total built-up area mentioned in the plan and divide it by the total plot area. Compare this against the maximum permissible FAR for your zone. In India, you can also check the RERA (Real Estate Regulatory Authority) registration details, which mandate disclosure of carpet area, built-up area, and super built-up area.