Carpet Area Calculator

When you buy a flat in India, the same home can be described by three different sizes, and the gap between them can be wide. Carpet area is the part you actually live on. The other two add walls, balconies and a share of the building's common spaces. This calculator moves between them so you can compare flats on the same basis.

Looking for carpet flooring rather than flat sizes? Add up your rooms with the floor area calculator, or see the tile calculator for flooring sold by the piece.

Formula

Carpet area = Built-up area × (1 − w ÷ 100)

w

walls and balcony as a percentage of built-up area, an assumption you can edit

Going the other way, built-up area = carpet area ÷ (1 − w ÷ 100). From a super built-up figure with loading L, built-up area = super built-up area ÷ (1 + L ÷ 100).

Carpet, built-up, super built-up and plinth area

Only carpet area has a definition in the national law described below. The others are trade terms, so a builder's exact usage can differ from the outline here, and the brochure's fine print is worth reading.

• Carpet area: the usable floor inside the flat.
• Built-up area: carpet area plus the space taken by external walls and shafts, and usually the balcony.
• Super built-up area: built-up area plus a share of common spaces such as lobbies, staircases and lift wells. It is sometimes called saleable area.
• Plinth area: generally the covered area at floor level, walls included. For a rough plinth area estimate, treat it as built-up area and enter it in that box, then check how your plan treats balconies.

What RERA means by carpet area

The Real Estate (Regulation and Development) Act, 2016, known as RERA, gives carpet area a specific meaning. In general terms, it is the net usable floor area of an apartment. That leaves out the area under external walls and service shafts, along with any exclusive balcony, verandah or open terrace, but it does count the area under internal partition walls.

Counting the internal partitions is the detail people miss. Informal usage sometimes measures only the open floor of each room, which gives a smaller number than the RERA figure for the same flat, so an old brochure and a new agreement may not match. An exclusive balcony is left out of carpet area, but that doesn't mean it comes free, so see how your agreement treats it.

This page is a general summary and not legal advice. The Act and your state's rules set out the exact wording, and your sale agreement is the document to check for the carpet area of your flat.

Built-up area to carpet area

Take off the percentage for walls and balcony. A flat with a built-up area of 1,200 sq ft and an assumed 18% comes to 1,200 × (1 − 18 ÷ 100) = 984 sq ft of carpet area, or about 91.42 sq m.

People often search for how to turn square feet into carpet area, but square feet is only the unit. What matters is which area the number describes. Before you enter a figure, find out whether it is the built-up or the super built-up size, then choose the matching method.

Carpet area to built-up area

Here you divide rather than multiply, because the percentage is a share of built-up area. A carpet area of 650 sq ft at 15% gives 650 ÷ 0.85 ≈ 764.71 sq ft of built-up area.

A common slip is to add the percentage to the carpet area. With 800 sq ft at 20%, adding gives 960 sq ft, while the correct built-up area is 800 ÷ 0.80 = 1,000 sq ft. The 20% applies to the larger number.

Super built-up area and loading

Loading is the extra area added for common spaces. Here it is entered as a percentage of built-up area. A flat sold as 1,500 sq ft with 25% loading has a built-up area of 1,500 ÷ 1.25 = 1,200 sq ft. At 20% for walls and balcony, its carpet area is 960 sq ft.

Some sellers quote loading on carpet area instead. To use that kind of figure, set walls and balcony to 0%, and the built-up row then shows the carpet area: 1,300 sq ft with 30% loading on carpet gives 1,300 ÷ 1.30 = 1,000 sq ft.

These sizes also change how a price reads. At ₹8,000 per sq ft of super built-up area, the 1,500 sq ft flat costs ₹1.2 crore. Divide that by its 960 sq ft of carpet area and you are paying ₹12,500 per sq ft of usable floor.

Choosing the percentages

No single percentage suits every building. Wall thickness, balcony size, the number of flats per floor and the amount of shared space all move these numbers, which is why they are open for editing. The 20% and 25% in the boxes are starting values to show the arithmetic and aren't market figures.

You will get a better number from your own building's documents. If a flat's papers give a carpet area of 880 sq ft and a built-up area of 1,100 sq ft, then walls and balcony are 1 − 880 ÷ 1,100 = 20%. Treat anything worked out from an assumed percentage as an estimate until you have the stated figure.

Frequently asked questions