A Bengaluru buyer eyeing an independent floor in a four storey building on a narrow lane could not understand why the seller kept mentioning something called FAR. It turned out the building had squeezed in more floors than the plot's rules allowed for that road, and that quiet excess was a legal problem hiding behind an attractive price. Floor Space Index, or FAR, is one of those technical terms buyers skip, yet it decides how much can legally stand on a plot, and whether what you are buying is fully within the rules.

The short answer. FSI, also called FAR, is the ratio of a building's total built-up floor area to the area of the plot it sits on, and it sets a legal limit on how much can be constructed. In Bengaluru it is governed by the building bye laws and varies mainly with the width of the abutting road, so a wider road generally allows a higher FAR. The trade off for a buyer is that a building exceeding its sanctioned FAR is in deviation, which can affect its legal standing, so verifying that the construction stays within the permitted FAR matters as much as the price.

What is FSI or FAR?

FSI, the Floor Space Index, and FAR, the Floor Area Ratio, refer to the same idea, the relationship between how much floor area a building has and the size of the plot it stands on. The formula is simple. FAR equals the total built-up area divided by the plot area. So a FAR of 1.5 on a 1,000 square foot plot means roughly 1,500 square feet of built-up area is permitted, before deductions for setbacks and parking. It is the rulebook's way of controlling how densely a plot can be developed.

Two deductions are worth understanding, because they mean the built-up area is not quite the whole story. Certain spaces, such as parking, basements used for services, and some common areas, may be treated differently in the FAR calculation, and the plot must also leave mandatory setbacks, the open margins around the building. So the floor area you can actually enjoy is shaped both by the FAR limit and by these rules on what counts and what must stay open. A buyer does not need to master the arithmetic, but should know that a builder cannot simply cover the whole plot to the boundary and stack floors freely, because the bye laws constrain both the ratio and the layout.

The two terms are often used interchangeably, with FAR usually written as a decimal ratio and FSI sometimes expressed as a percentage of the same relationship. For a buyer the distinction in wording does not matter. What matters is the single number that tells you the maximum floor area the authorities allow on that plot, because everything built above that limit is construction the rules did not sanction.

How is FSI decided in Bengaluru?

In Bengaluru, FSI is regulated by the building bye laws, and the single biggest factor that sets it is the width of the road the plot abuts. Broadly, a plot on a wider road is allowed a higher FAR than a similar plot on a narrow lane, because wider roads can support denser development. The permissible FAR therefore differs from plot to plot depending on its road, which is why two plots of the same size can carry very different building limits.

Because the exact figures are set by the authorities and are revised over time, treat any specific FAR number as something to confirm rather than assume. The permissible FAR for a particular plot depends on its zone, its road width, and the current bye laws, so the reliable way to know a plot's limit is to check it against the applicable regulations for that location. Do not rely on a builder's claim about how much can be built without checking the basis for it.

Why does FSI matter to a buyer?

It matters because it separates legal construction from deviation. If a building has been constructed within its sanctioned FAR, the floors and the flat you are buying are part of an approved structure. If the builder has exceeded the permitted FAR, adding floors or area beyond what was sanctioned, that excess is a violation, and violations carry consequences, from difficulty getting an occupancy certificate to problems with the property's civic standing and, in serious cases, exposure to action on the unauthorised portion.

This connects directly to other checks a Bengaluru buyer should make. A building that overshot its FAR is exactly the kind of property that can end up with compliance problems, which in turn can affect its khata status and its financing. So FSI is not an abstract planning concept, it is a practical filter for whether the home you are buying stands on solid legal ground or on an excess the rules never approved.

The risk is sharpest in the upper floors of a building. When a developer exceeds the sanctioned FAR, the extra area is often the topmost floors or an added portion, and those are precisely the units most exposed if the deviation is ever acted upon. A buyer who unknowingly purchases a flat that sits within the unauthorised excess can find themselves holding the part of the building with the weakest legal footing. This is why it is not enough to know the building looks complete and occupied. What matters is whether your specific flat falls within the sanctioned area or within the part that was built beyond the permitted FAR.

What is premium FAR?

Premium FAR is additional floor area that a developer can obtain beyond the base entitlement by paying a charge to the authorities. Rather than being free, this extra building capacity is purchased, typically linked to the value of the additional area, and it is one of the ways cities encourage denser, vertical growth along corridors that can support it, such as major roads and transit lines. For a buyer, the relevant point is that legitimate extra FAR is sanctioned and paid for, not simply added.

The distinction to hold on to is between paid, approved premium FAR and unauthorised excess. A building that has properly obtained and paid for additional FAR is within the rules for that higher limit. A building that has simply built beyond its entitlement without such sanction is in deviation. Since the schemes and charges for premium FAR are set by the authorities and change over time, confirm the current position and whether a given building's extra area is properly sanctioned.

How should a Bengaluru buyer check FSI compliance?

Start from the sanctioned plan. Ask for the approved building plan and compare what was sanctioned with what has actually been built, because the gap between the two is where FAR violations live. Check the number of floors and the built-up area against the approval, and confirm the plot's permissible FAR for its road and zone under the current bye laws. Where the built structure matches the sanction, you are on firm ground.

Where anything looks larger than sanctioned, treat it as a red flag and get it examined before you commit. A professional, an architect or a lawyer familiar with the local bye laws, can verify whether a building is within its FAR or has deviated. Because the rules are technical and location specific, this is one area where expert verification is worth the cost, since the consequences of buying into an FAR violation fall on the owner, which will be you.

Your seven step FSI verification checklist

1. Ask for the sanctioned building plan for the property.
2. Note the plot area and the built-up area actually constructed.
3. Confirm the permissible FAR for the plot's road width and zone.
4. Compare the built area against the sanctioned FAR and plan.
5. Check whether any extra area is properly sanctioned premium FAR.
6. Treat construction beyond the sanction as a deviation to investigate.
7. Have an architect or lawyer verify compliance before you commit.

Frequently asked questions

What is FSI or FAR in simple terms?

FSI, or FAR, is the ratio of a building's total built-up floor area to the area of the plot it stands on. It sets the legal limit on how much can be constructed on that plot. The formula is simply the total built-up area divided by the area of the plot.

How is FSI decided in Bengaluru?

In Bengaluru, FSI is governed by the building bye laws, and the main factor is the width of the road the plot abuts, with wider roads generally allowing a higher FAR. The permissible figure also depends on the zone and the current rules, so confirm the exact FAR for a specific plot against the applicable regulations.

Why does FSI matter when buying a flat?

Because it separates legal construction from deviation. A building within its sanctioned FAR is approved, while one that exceeds the permitted FAR has unauthorised area, which can cause problems with the occupancy certificate, civic standing, and financing. Checking that a building stays within its FAR helps confirm the home you are buying stands on solid legal ground.

What is premium FAR in Bengaluru?

Premium FAR is additional floor area a developer can obtain beyond the base entitlement by paying a charge to the authorities, typically linked to the value of the extra area. It is a legitimate, paid way to build more along corridors that support density. It is different from unauthorised excess, which is built without such sanction and remains a deviation.

For related Bengaluru reading, see our guide to how A Khata and B Khata reflect a property's compliance, and our explainer on the occupancy certificate and completion certificate. The specific FAR figures and premium FAR charges are set by the authorities, so confirm them for your plot.

Last updated 26 July 2026. PropNewz Team.