FSI vs FAR in India: The Formula, the Terminology and What Actually Varies

Direct answer: FSI (Floor Space Index) and FAR (Floor Area Ratio) express the same idea — permitted floor area divided by plot area. In Indian practice FSI is usually written as a ratio (1.75) and FAR sometimes as a percentage (175%). The number is not the hard part. What varies between authorities is which areas count towards it, which plot area you divide by, and what you can add on payment. Treat every FSI figure as an assumption until you have read the applicable development control regulation for that plot.

The formula

FSI = Total permitted floor area (all floors) ÷ Net plot area
Permitted floor area = FSI × Net plot area

Worked at its simplest: a net plot of 10,000 sq ft with a permitted FSI of 1.75 yields 17,500 sq ft of countable floor area. If a local regulation additionally permits 0.5 FSI on payment of a premium, the theoretical envelope becomes 2.25 × 10,000 = 22,500 sq ft — subject to height, setback, parking and coverage rules actually allowing it to be built.

The vocabulary that decides the answer

• Gross plot area — the area as per title/survey documents, before deductions.
• Net plot area — gross area minus road widening, reservations, DP road setbacks, nala/canal buffers or handed-over portions. FSI is normally applied to the net figure. Confirm the definition in the applicable regulation.
• Countable (chargeable) FSI area — floor area that consumes the index.
• Free-of-FSI / non-chargeable area — items an authority excludes: commonly some circulation, service areas, refuge floors, parking floors, and specified ancillary areas. Exclusion lists differ substantially between states and change over time. The Model Building Bye-Laws, 2016 published by the Ministry of Housing and Urban Affairs illustrate the structure of such exclusions, but they are a model for states to adopt or adapt, not a binding national list. Itemise the exclusions from the dated clause of the regulation governing your plot.
• Ground coverage — the proportion of plot footprint that may be built upon. A generous FSI with tight coverage forces height; tight height with generous FSI forces a larger footprint.
• Base / permissible / premium / TDR / incentive FSI — separate layers. Only the base layer is available unconditionally.

Why FSI alone never gives you saleable area

FSI is a planning number. Revenue is earned on saleable area, which is derived from FSI area after design losses and after adding whatever loading the local market accepts. The chain is:

Net plot area → permitted FSI area → constructible built-up area
→ efficient carpet area → market saleable area (carpet × loading)

Two projects on identical FSI can differ by 10–15% in saleable output because of core sizing, corridor length, parking ramp geometry, refuge and service planning. See the companion drafts on development efficiency (https://devpartner.in/insights/development-efficiency-fsi-to-saleable) and gross vs net saleable area (https://devpartner.in/insights/gross-built-up-vs-net-saleable-area).

What varies by authority — the checklist to verify per site

1. Which regulation governs the plot: state DCR/UDCPR-type rules, metropolitan/development-authority rules, municipal building bye-laws, or a special planning authority.
2. Base FSI for the land use and plot size band.
3. Road-width linkage — many regimes step FSI with abutting road width.
4. Whether FSI is on gross or net plot area, and which deductions apply.
5. Free-of-FSI items and any cap on them.
6. Availability, quantum and cost of premium/chargeable FSI and TDR loading.
7. Height controls, including airport/heritage/coastal constraints.
8. Parking standard and whether parking floors are FSI-free.
9. Whether the plot is affected by amalgamation, layout approval or master-plan revision.

There is no national FSI rule. In India, land use and building regulation are administered by state governments and local planning authorities; the Union government issues model bye-laws and planning guidance only. Every FSI figure used in a live appraisal must therefore cite the dated clause of the governing development control regulation or building bye-law for that specific jurisdiction.

Using FSI in early feasibility

Early-stage feasibility does not need a sanctioned plan; it needs a defensible band. Practice:

• Model three FSI scenarios: conservative (base only), central (base + likely non-chargeable benefit), and upside (base + premium/TDR at a costed rate).
• Record each scenario's assumption source and date next to the number.
• Never carry an upside FSI into a land offer without pricing the premium payment, the extra parking, the extra structure and the longer approval timeline.
• Convert FSI to saleable area using an explicit efficiency assumption, not a habit.

You can lay this out quickly with the DevPartner FSI/FAR calculator (/fsi-far-calculator) and stress it in development potential (/development-potential).

Common mistakes

• Quoting FSI from a neighbouring project. Approvals are date-stamped; the regime may have changed.
• Applying FSI to gross plot area when the regulation says net — a 6% road setback silently inflates the appraisal.
• Treating free-of-FSI area as free area. It is free of index, not free of cost. It still consumes structure, finishes and time.
• Adding premium FSI without adding parking. This is the single most common way a "better" scheme becomes unbuildable. See https://devpartner.in/insights/parking-feasibility-before-design.
• Assuming FSI upside is transferable to price. Absorption and unit mix limits, not the index, often cap revenue.

Feasibility checklist

• [ ] Governing regulation identified, with clause reference and date
• [ ] Gross vs net plot area reconciled to title/survey
• [ ] Base FSI band recorded with source
• [ ] Free-of-FSI treatment noted as assumption
• [ ] Premium/TDR quantum and cost recorded separately
• [ ] Height, coverage and setback cross-checks done
• [ ] Parking standard applied to the scenario FSI, not the base
• [ ] FSI → saleable conversion efficiency stated explicitly

FAQs

Is FSI the same as FAR? Conceptually yes. The difference is expression (ratio vs percentage) and local drafting convention, not arithmetic.

Can FSI be increased? In many regimes additional buildable area is available through premium payment, TDR, or incentive provisions for specified project types. Availability, quantum and price are jurisdiction- and date-specific, and must be read from the notified schedule of the competent authority on the date of appraisal.

Does balcony area count? Treatment of balconies, service ducts and terraces varies by regulation and has changed in several states. Verify the clause; do not generalise.

What FSI should I use for a first-pass land appraisal? The conservative base figure, with the upside modelled separately and clearly labelled.

Next step

Run the site through the FSI/FAR calculator (/fsi-far-calculator), then carry the output into a residual land value test (/residual-land-value-calculator) so the planning assumption is visibly connected to the price you can pay.

Sources

• Model Building Bye-Laws, 2016 — Ministry of Housing and Urban Affairs, Government of India (accessed 6 August 2026): https://mohua.gov.in/cms/model-building-byelaws.php

This article states no jurisdiction-specific rate, fee or market figure as fact. Every number in it is either arithmetic on stated assumptions or an explicitly labelled assumption.

Disclaimer. This article is decision support, not planning or legal advice. Floor-area rules, exclusions, premium mechanisms, parking standards, setbacks, approvals, taxes, finance terms and market inputs vary by jurisdiction and change over time. Verify every figure with the applicable development control regulations and with qualified architects, licensed surveyors, legal counsel and the competent statutory authority before committing capital.

Methodology and assumption handling: `/methodology`.