The Floor Space Index Calculator helps architects, developers, city planners, and property owners determine how much floor area can be constructed on a plot of land. Also known as FAR (Floor Area Ratio), the Floor Space Index (FSI) is a regulatory tool used by local building authorities to control urban development, maintain density, and ensure infrastructure capacity is not overwhelmed.
By entering the total built-up area and the plot area, this calculator instantly returns the FSI value. This allows users to verify whether their planned construction adheres to local zoning rules or if they need to modify their project. It is an essential tool in real estate planning, urban layout analysis, and property investment decisions.
This tool belongs to the real estate regulation and planning calculator category and supports efficient use of land while ensuring legal compliance in construction projects.
formula of Floor Space Index Calculator
FSI (or FAR) = Total Built-up Area / Total Plot Area
Where:
Total Built-up Area = Sum of all constructed floor areas (in square meters or square feet)
Total Plot Area = The area of the land parcel (in the same unit as the built-up area)
Extended Breakdown for Multi-Floor Buildings:
Total Built-up Area = Σ (Area of Each Floor)
Then:
FSI = (Area of Floor 1 + Area of Floor 2 + … + Area of Floor n) / Plot Area
Important note: Different municipalities may have rules about what counts toward the built-up area. Balconies, basements, parking, and common areas might be partially or fully excluded depending on local codes.
Helpful Reference Table: FSI Standards and Usage Rights
This table shows general FSI limits used in urban planning across different zones. While actual values depend on local zoning laws, this gives a practical idea of what to expect.
| Zone Type | Typical FSI Limit | Description/Use |
|---|---|---|
| Residential Low-Density | 1.0 | Single-family homes, garden spaces |
| Residential High-Density | 2.0 – 3.0 | Apartments, multi-story residential complexes |
| Commercial Core Area | 3.0 – 5.0 | Office buildings, shopping centers |
| Industrial Zones | 1.5 – 2.0 | Warehouses, manufacturing facilities |
| Transit-Oriented Zones | Up to 6.0 | Near metro/train stations for high-rise development |
Always refer to your city’s development control regulations (DCR) for official FSI limits.
Example of Floor Space Index Calculator
Let’s say you own a plot of land that measures 500 square meters.
You plan to build:
- Ground Floor: 200 m²
- First Floor: 200 m²
- Second Floor: 100 m²
Step 1: Add total built-up area
Total Built-up Area = 200 + 200 + 100 = 500 m²
Step 2: Apply the formula
FSI = 500 / 500 = 1.0
In this case, you’re using 100% of the allowable FSI if the local limit is 1.0. If your city allows up to 1.5 FSI, you can still build up to 750 m² in total floor area.
Most Common FAQs
A typical FSI for residential plots ranges from 1.0 to 2.5 depending on the city's infrastructure and planning policies. A higher FSI means more floors or larger floor areas can be built.
It depends on local regulations. In many cases, covered parking, basements used for storage or parking, and open terraces are excluded or only partially counted toward FSI.
A higher allowable FSI generally increases the value of a plot because it permits more construction and therefore higher return on investment, especially in commercial and multi-family housing zones.