Floor Space Index (FSI)
The ratio of total built-up floor area to the plot area. Also called Floor Area Ratio (FAR). Determines how much construction is legally permitted on a given plot.
What is Floor Space Index (FSI)?
Floor Space Index (FSI) — identical in meaning to Floor Area Ratio (FAR) — is the ratio of a building's total built-up area across all floors to the area of the plot on which it stands. A plot of 10,000 sqft with an FSI of 2.5 permits a maximum of 25,000 sqft of built-up area, which could be distributed across multiple floors.
FSI = Total Built-Up Area of Building ÷ Plot Area
FSI is set by the local development authority and varies by zone type (residential, commercial, mixed-use), plot size, proximity to metro stations or roads, and city-level master plan regulations. It is the single most important determinant of a project's density and tower height.
FSI by City (2026)
| City / Zone | Base FSI | Maximum (with premium) |
|---|---|---|
| Bangalore (residential) | 2.5 | 3.25 (premium FSI) |
| Bangalore (near metro, TDR) | 3.25 | 4.0 |
| Mumbai (residential) | 3.0 | 5.0 (near metro/road) |
| Mumbai (affordable housing) | 4.0 | 5.0 |
| Delhi NCR (residential) | 2.0 | 3.5 |
| Hyderabad (HMDA zone) | 2.0 | 3.0 |
| Pune (PCMC) | 1.5 | 2.5 |
Premium FSI in Karnataka
Karnataka introduced the concept of premium FSI (also called incentive FSI) where builders can purchase additional FSI beyond the base entitlement by paying a premium to the BBMP or BDA. This premium goes into a public infrastructure fund. Premium FSI in Bangalore can add 0.5 to 1.0 over the base FSI, enabling taller towers. Buyers benefit through more units (lower per-unit land cost); the risk is higher density and potential infrastructure strain in the locality.
Why FSI Matters for Buyers
Higher FSI means more floors, more units, and typically more amenities funded by the greater number of buyers sharing common costs. However, very high FSI projects (4.0+) in areas with inadequate roads, water supply, and drainage can create livability problems. The FSI consumed by a project versus the permissible maximum also signals whether the builder has room for additional phases or has fully exploited the plot.
How Brickplot Uses FSI
Brickplot checks FSI compliance for every project — whether the total built-up area of approved plans exceeds the permissible FSI for that zone. Projects with suspected excess FSI (a signal of encroachment or unauthorised floors) are flagged under the Governance & Approvals axis and trigger a manual review before scoring.
Related Terms
- Floor Area Ratio (FAR) — same concept, Delhi/NCR terminology
- Building Plan Approval — the authority that sanctions FSI use
- Commencement Certificate — issued after FSI-compliant plan is approved
Related terms
Brickplot verifies floor space index (fsi) disclosures on every reviewed project as part of the independent 11-axis score. No builder commissions. No editorial override.