Floor Space Index (FSI)
Floor Space Index (FSI), also called Floor Area Ratio (FAR), is the ratio of the total built-up floor area of a building to the area of the plot on which it stands, determining the maximum permissible construction density in a given zone.
FSI is one of the most consequential planning tools in Indian urban governance. It governs how much a developer can build on a given piece of land and therefore directly influences land prices, housing supply, and rental yields. The formula is straightforward: FSI equals the total floor area of all floors divided by the plot area. If a 1,000 sq ft plot has an FSI of 2, the developer may construct up to 2,000 sq ft of built-up area spread across any number of floors that local building bylaws permit.
City-wise variation is substantial and reflects each municipal body's planning philosophy. Mumbai (Brihanmumbai Municipal Corporation) historically maintained a base FSI of 1.0 to 1.33 across most island-city wards, contributing to its notoriously congested housing stock and stratospheric land values. The Maharashtra government began revising this framework significantly from 2018 onward, allowing base FSI of 2.5 for island city redevelopment and up to 5.0 along metro corridors under the new Development Control and Promotion Regulations (DCPR 2034). Pune's Development Plan allows an FSI of 1.5 for most residential zones, with premiums available for purchase. Bengaluru (BBMP) offers FSI of 2.25 to 3.25 depending on road width and zone. Delhi follows FAR norms under the Master Plan for Delhi 2041, ranging from 1.2 to 3.5 across mixed-use, residential, and commercial zones.
Premium FSI is an additional construction rights mechanism where developers pay a fee to the municipal body for FSI above the base entitlement. In Maharashtra, the premium is charged as a percentage of the Ready Reckoner rate of the land. This has become a significant revenue source for municipal corporations and has partly democratised access to density rights without requiring outright land acquisition.
From an investor and home-buyer perspective, understanding FSI is critical for assessing redevelopment potential of old properties, evaluating Society Redevelopment or Self-Redevelopment proposals, and understanding why new projects in metro-rail influence zones command higher unit prices even on smaller floor plates. An area undergoing FSI liberalisation tends to see a rerating of land values as the development potential per square foot of land increases. RERA-registered projects must disclose the permissible and consumed FSI in their project disclosures, giving buyers a tool to verify that developers are not violating sanctioned plans.