Key Difference:   FSI (Floor Space Index) and FAR (Floor Area Ratio) are unified development codes applicable in cities. This ratio is obtained by dividing the build-up area of a building to the total size of the plot. Therefore, both FSI and FAR are the same.

FSI stands for Floor Space Index, whereas FAR stands for Floor Area Ratio. FSI and FAR are both related to the field of real estate. FSI and FAR both represent the calculation based on the ratio derived by dividing the Gross floor area with the total size of land on which the building is made. The terms may also be used in context to certain limitation attached with these terms.

Thus, simplly FAT or FSI = Gross floor area/ Area of the plot

Gross floor area includes area of all floors just leaving those areas which are exempted under certain regulations. The concept of FSI or FAE got introduced in America. It was introduced for the building control. Architects make their designs based on these important ratios. It is important to mention that FSI and FAR are the same. However, Indians prefer to use theterm FAR on FSI, whereas other countries use FAR more frequently.

Higher value of FAR or FSI means more dense construction, whereas a lesser value indicates a sparse type of construction. An FSI or FAR of 2.0 would means that total floor areas is twice the gross area of the plot, and therefore it clearly means that this type of FAR suggests a multiple-store building.

According to the FSI or FAR, the builders get the flexibility to decide whether they want a low building covering most of the plot are or a tall building covering a small portion of the plot. FAR or FSI has been an important unified development code used in the field of real estate. These codes are applicable to the buildings in almost every city. There are certain other limitations attached with them like a minimum required front open space, etc. The number of floors is generally specified in context to FSI or FAR.

Comparison between FSI and FAR :

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