A buyer comparing two apartments in Bengaluru noticed that one building had a floor more than the neighbouring project on a similar plot, and the price per square foot was suspiciously low. The extra floor was not a bonus. It turned out the builder had constructed beyond the floor area the plot was allowed, and that single fact hung over the building's occupancy certificate and the buyers' home loans. Understanding one planning number, the FSI, would have told her what to ask before she fell for the deal.

The short answer. FSI, the floor space index, and FAR, the floor area ratio, are the same planning number: the ratio of a building's total built-up area to the plot area, which decides how much can legally be built on a plot. In Bengaluru the applicable figure is set by the building bylaws and depends on the zone, the plot size, and the width of the abutting road, and builders can add buildable area through mechanisms such as premium FAR. The trade off for a buyer is that a building constructed beyond its sanctioned FSI is a deviation, and that deviation can block the occupancy certificate and complicate a home loan, so the buildable area a project used is something to verify, not admire.

What are FSI and FAR, and are they the same thing?

FSI and FAR are two names for the same metric, so you can treat them as interchangeable. The floor space index and the floor area ratio both express the relationship between how much floor area a building has and how large its plot is, and different cities simply prefer different labels for the same idea. The number tells you how intensively a plot may be built up: a higher FSI means more floor area is permitted, and a lower one means less. For a home buyer, the value of understanding it is not to become a planner but to grasp the ceiling that applied to the building you are considering, because everything about its legality flows from whether it stayed within that ceiling. A project that respected its FSI is on solid ground, while one that exceeded it carries a problem that can surface at the worst time. It is worth remembering that the FSI is a legal ceiling, not a marketing feature, so a taller or denser looking building is not automatically better value. If anything, unusually generous construction on a small plot or a narrow road is a prompt to check the sanctioned plan closely, because that is exactly the pattern an unauthorised extra floor tends to produce.

How is the buildable area calculated?

The buildable area is the plot area multiplied by the FSI, which gives the total floor area permitted across all floors. If a plot has a given FSI, you multiply the plot's area by that number to get the maximum built-up area the building may have in total. To see the mechanics with an illustrative figure, a plot of 500 square metres with an FSI of 2.0 would permit 1,000 square metres of total built-up area combined across the floors. The actual FSI for a specific plot is whatever the bylaws assign, so treat that 2.0 purely as an example of the arithmetic rather than a figure to apply to your plot. What matters is the principle: the permitted floor area is a direct product of the plot size and the FSI, and a building that shows far more floor area than that product should prompt questions.

What determines the FSI for a plot in Bengaluru?

In Bengaluru the FSI for a plot is set by the building bylaws and varies with the zone, the plot size, and the width of the abutting road. Broadly, a wider road and a more intensively planned zone allow a higher FSI, while a narrow road and a low density zone allow less, because planning tries to match building intensity to the infrastructure that serves it. The regulatory framework, administered through the Bangalore building bylaws, is what fixes the number for any given plot, so the reliable figure is the one the bylaws and the sanctioned plan specify rather than a rule of thumb. Because these values are set by regulation and can change, a buyer should look at the sanctioned plan for the actual FSI the project was granted, and check it against what was built. Do not rely on a generic range you read online for a specific building.

Why does FSI matter to a home buyer?

FSI matters because a building that exceeds its sanctioned floor area is in deviation, and that deviation can block the occupancy certificate and unsettle your loan. When a builder constructs more floor area than the plot's FSI allowed, the excess is unauthorised, and the authorities can withhold the occupancy certificate that certifies the building is lawfully complete and fit to occupy. A missing occupancy certificate, in turn, can make banks wary and can expose owners to penalties or demolition risk for the unauthorised portion. This is why the extra floor in our opening example was a warning rather than a windfall. For a buyer, FSI is the number that connects a physical building to its legal standing, and confirming that a project stayed within its sanctioned FSI is part of the same due diligence as checking the occupancy certificate and the sanctioned plan.

What are premium FAR and TDR?

Premium FAR and transferable development rights, or TDR, are legitimate mechanisms that let a builder add buildable area beyond the base FSI. Premium FAR allows a developer to buy additional floor area from the government, within limits set by the rules, typically along corridors with better infrastructure. TDR lets development rights generated elsewhere, for example where land was surrendered for a public purpose, be loaded onto another plot to increase its buildable area. These are lawful ways to build more, and their existence is why two similar plots can legitimately carry different amounts of construction. The key point for a buyer is the difference between extra area that was lawfully obtained through premium FAR or TDR and reflected in the sanctioned plan, and extra area that was simply built without authorisation. The first is fine, the second is a deviation, and only the sanctioned plan tells you which one you are looking at.

FSI and related terms at a glance

Buyers meet several related terms, so here is what each one means.

The dividing line that runs through the table is authorisation: extra area that appears on the sanctioned plan is fine, while extra area that does not is a deviation.

What should a buyer check about FSI compliance?

A buyer should check that what was built matches what the sanctioned plan permitted, using the plan and the occupancy certificate together. Work through these checks before you commit.

1. Ask for the sanctioned building plan and note the FSI and floor area it permits.
2. Compare the number of floors and the built-up area on the ground against that plan.
3. Confirm that any extra area is backed by premium FAR or TDR reflected in the plan.
4. Check that the project holds an occupancy certificate, which signals the build was accepted as lawful.
5. Look for any deviation notice, penalty, or regularisation history on the property.
6. Verify the abutting road width and zone match the assumptions behind the sanctioned FSI.
7. Ask your lawyer and your bank whether they see any FSI related issue before you pay.

If the built area clearly exceeds what the plan allowed and there is no premium FAR or TDR to explain it, treat that as a serious issue and get it clarified before you proceed, rather than after.

Frequently asked questions

Are FSI and FAR the same thing?

Yes. FSI, the floor space index, and FAR, the floor area ratio, are two names for the same planning metric, the ratio of a building's total built-up area to its plot area. Different cities use different labels, but the calculation and meaning are identical, and both decide how much floor area may be built on a plot.

How is buildable area calculated from FSI?

You multiply the plot area by the FSI to get the maximum total built-up area permitted across all floors. For example, using an illustrative FSI of 2.0, a 500 square metre plot would permit 1,000 square metres of built-up area. The FSI that actually applies is the one the bylaws and sanctioned plan assign to that specific plot.

What decides the FSI for a plot in Bengaluru?

The FSI is set by the Bangalore building bylaws and depends on the zone, the plot size, and the width of the abutting road, with wider roads and denser zones generally allowing more. Because these values are regulated and can change, a buyer should rely on the sanctioned plan for the actual FSI a project was granted rather than a generic online range.

What happens if a building exceeds its sanctioned FSI?

Construction beyond the sanctioned FSI is a deviation, and the unauthorised area can lead the authorities to withhold the occupancy certificate and impose penalties. That in turn can make banks reluctant to lend and expose owners to risk over the unauthorised portion. This is why buyers verify that the built area matches the sanctioned plan before purchase.

Pair this with our guides to verifying a sanctioned building plan and spotting deviations and the difference between an occupancy certificate and a completion certificate. If you are comparing projects, our overview of Embassy Codename Yelahanka shows the approvals worth checking. The applicable rules sit with the BBMP building bylaws.

Last updated 2026-07-13. PropNewz Team.