PLOTTU

FSI Calculator

Estimate permissible floor space index and buildable area for a plot.

Enter Plot Details
Provide plot metrics, land use, and special conditions to estimate FSI.

Auto convert to sq.m / meters

Convert sqft and feet inputs automatically.

Special Conditions

This calculator provides indicative FSI based on inputs. Local approvals and site-specific conditions can override these values.
FSI Summary
View the estimated FSI and buildable floor area.
Enter required plot values to see the calculation.
Notes & Assumptions

FSI values are indicative and based on Tamil Nadu Combined Development and Building Rules patterns.

Premium FSI increases are applied on top of base FSI. Confirm eligible charges with local authorities.

Setbacks, parking, and special restrictions (CRZ, CBA, aquifer) may reduce permissible built-up area.

FSI Guide
Key definitions, regulations, and planning considerations.

What is FSI?

Floor Space Index (FSI) or FAR is the ratio of total covered floor area to plot area. FSI = Total plinth area on all floors / Plot area. It sets the maximum buildable area on a site.

Current Tamil Nadu ranges

Non-high rise buildings up to 18.3m typically allow FSI up to 2.0. High-rise buildings depend on road width (12m: 2.0, 15m: 2.5, 18m+: 3.25). These values can vary by authority updates.

Premium FSI

Premium FSI allows additional floor area above base FSI by paying charges. Typical bands are 30%, 40%, or 50% based on road width and land use. Metro corridors within 500m often receive a 50% discount on premium charges.

Setbacks & coverage

Setbacks vary with road width, building height, and category. Even if FSI permits higher floor area, ground coverage and setbacks can limit practical buildable area.

Excluded areas

Staircase/lift rooms, open stilt parking, basement parking, service ducts, and limited service verandahs may be excluded from FSI computation under state rules.

FSI FAQ
Answers to common planning questions.

How is max buildable area calculated?

Multiply plot area by applicable FSI. Example: 2,400 sq ft plot with FSI 2.0 gives 4,800 sq ft total floor area.

Does premium FSI apply everywhere?

Premium FSI depends on local authority rules, road width, and land use. It may be restricted in CRZ, aquifer zones, or special conservation areas.

What is the impact of high-rise designation?

High-rise buildings (over 18.3m) require wider roads, larger setbacks, and additional approvals. FSI eligibility depends on road width thresholds.

Are CBA or EWS plots treated differently?

Continuous Building Areas and EWS layouts may allow relaxed setbacks and maintain FSI around 2.0, subject to local planning notifications.

Why does the calculator ask for frontage and depth?

Non-rectangular plots should use the largest possible rectangle. Frontage and depth guide coverage feasibility and setback checks.

Do parking areas count toward FSI?

Open stilt parking, basement parking, and stair/lift rooms serving parking floors are typically excluded, but confirm with the local rulebook for your project.

What approvals should I verify?

CMDA, DTCP, or municipal approvals can change permissible FSI and premium allowances. Always validate with the latest local circulars.