Built Up Area vs Carpet Area: What You Pay For

What is the difference between built up area vs carpet area?

In short: Carpet area is the floor you can actually lay a carpet on. Built-up area adds the thickness of the walls and usually a balcony. UP RERA has told developers to sell on carpet area only.

Checked 15 October 2026. If you have been quoted a rate per sq ft and cannot tell which area it applies to, you are not being slow. The trade uses three names for the same flat, and the number changes with each. To see what stamp duty and registration add to that price, the Lucknow stamp duty calculator works it out from the circle rate.

A flat has one set of walls and one front door, but a brochure can describe its size three different ways. The bigger the number, the smaller the rate per sq ft looks. That is the whole reason the argument exists. The label moved, not you.

Carpet area, built-up area and super built-up area in plain words

Start from the inside of the flat and walk outwards.

Carpet area is the usable floor inside the flat. Bedrooms, kitchen, bathrooms, the living room, the passage between them. The thickness of the outer walls is not in it. Neither is the balcony.

Built-up area is carpet area plus the space the walls take up, and usually the balcony or a utility space too. It is bigger than carpet area because it measures the flat as a structure, not as a floor you can walk on. Builders use it as a trade term. The RERA clause we read, below, defines carpet area only.

Super built-up area is built-up area plus your share of the common parts: lobby, staircase, lift shaft, corridor, sometimes the clubhouse. You do not own a separate piece of the lobby. You are paying for a slice of it, spread across every flat in the tower.

How the three measures differ

Our view: the two bigger numbers are not lies. They are measures of something real. The trouble starts when a price per sq ft is quoted on the biggest number and the buyer compares it with a price per sq ft on the smallest.

What does RERA say about carpet area?

The law gives carpet area a definition. Section 2(k) of the RERA Act, 2016, as quoted by TaxGuru, calls it "the net usable floor area of an apartment, excluding the area covered by external walls," the areas under service shafts, exclusive balcony or verandah area and exclusive open terrace area, "but includes the area by the internal partition walls of the apartment."

Read that twice, because two details matter. The internal walls are inside the number. The balcony is outside it. So a RERA carpet area can be a little larger than the "carpet area" some older brochures described.

Uttar Pradesh went further. In January 2024 UP RERA directed developers to sell units on carpet area only, as The Week reported from a PTI story dated 3 January 2024. Its chairman said "There is no abbreviation or definition of Super Area in the RERA Act." Republic reported that selling on any other basis is deemed illegal, and that the model agreement for sale on the UP RERA portal is also based on carpet area.

So what do you do when a brochure still shows a super built-up figure? You treat it as marketing. The agreement you sign is the document that counts, and it should state carpet area. We cannot tell you how a particular builder prints its cost sheet today. Ask for it and read it.

A worked example: one flat, three rates

These numbers are made up to keep the sums easy. They are not a real flat or a real price. Real flats are larger, but the logic is identical.

Say a flat has 200 sq ft of carpet area. The walls take 25 sq ft and the balcony another 25. Built-up area is 200 + 25 + 25 = 250 sq ft. The builder adds a 150 sq ft share of lobby, stairs and lift, and calls the total super built-up area: 250 + 150 = 400 sq ft.

Now suppose the quoted rate is 10,000 per sq ft on super built-up area, and you pay on 400 sq ft. What are you paying per sq ft of floor you can use? The 400 sq ft you pay for is twice the 200 sq ft you can walk on, a 2:1 ratio. So the real rate is twice the quoted one.

The same flat, measured three ways

That 2:1 gap is deliberately heavy so you can see it. In a real tower the gap is smaller. But the method does not change, and it is the one check worth doing at the cost-sheet stage: divide the total price by the carpet area, and compare flats on that number.

One more thing. Never compare a rate per sq ft from one project with a rate from another unless both are on carpet area. A project that looks cheaper on paper can cost more per usable sq ft. The mistake is easy to make when every brochure picks its own measure, and the fault is the missing standard, not the buyer.

Does built-up area still matter?

Sometimes, yes. A resale flat or an older building may only have a built-up figure on its papers, and you cannot assume every seller will quote carpet area.

If you are looking at one of those, ask which walls and which balcony the number counts. Then work out the carpet area yourself with a tape measure, room by room. Length times width for each room, added up, gives you the floor you would actually live on.

For anything under construction in Uttar Pradesh, carpet area should be the one on the agreement. A RERA-registered project lists its details on the UP RERA portal, and the carpet area for each unit type should match what you are shown. If it does not, that is a question for the builder before you pay anything.

What to ask the builder before you pay a token

A short list, in the order we would ask it:

1. What is the carpet area of this exact unit, in sq ft, as it will appear in the agreement for sale?
2. Is the balcony or terrace counted, and at what rate? An exclusive balcony is not carpet area under the Act, so how it is priced should be written down.
3. What is the total price, and how does it break down in the cost sheet? Ask for the cost sheet in writing.
4. Does the carpet area match what the UP RERA registration shows for this project?
5. What does the price include besides the flat: parking, club membership, maintenance deposit?

If the answer to the first question is a super built-up figure, ask again for carpet area. A builder who cannot give it has told you something.

Area is only one of the things to confirm before money moves. Title, encumbrance and court records matter too, and we do that as a paid property verification, with only the first check free.

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