Floor Area Ratio Calculator

What Is a Floor Area Ratio Calculator?

A floor area ratio calculator helps buyers and developers compare carpet area, built-up area, super built-up area, and key real estate indices like FAR (floor area ratio), FSI (floor space index), loading factor, and open space ratio. These metrics clarify how much usable space you get versus what a builder advertises.

Key Area Definitions

Carpet area is the net usable floor space inside walls where you can lay carpet. Built-up area adds wall thickness to carpet area:

$$ \text{Built-up area} = \text{Carpet area} + \text{Wall area} $$

Super built-up area adds a proportional share of common spaces like lobbies, stairs, and lifts:

$$ \text{Super built-up} = \text{Built-up area} + \frac{\text{Common area}}{\text{Number of units}} $$

Floor Area Ratio and Loading Factor

The floor area ratio (FAR) or floor space index (FSI) measures total construction against total land:

$$ \text{FAR} = \frac{\text{Total built-up area}}{\text{Total land area}} $$

The loading factor shows how much common area is loaded onto each unit relative to carpet area:

$$ \text{Loading factor} = \frac{\text{Super built-up area}}{\text{Carpet area}} - 1 $$

For room-level flooring estimates, use the Flooring Calculator or Square Footage Calculator.