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Carpet area, built-up and super built-up: what you are actually buying

11 September 2026 · 5 min read

Three numbers describe the same flat and they can differ by a third. What each one means, why RERA forced the change, and how to work out the loading on a quoted price.

A flat advertised at a thousand square feet may give you seven hundred to live in. Nothing dishonest has necessarily happened — three different measurements are in circulation, and the largest of them is the one that used to appear in advertisements.

The three measurements

TermWhat it covers
Carpet areaThe usable floor inside the flat — what you could actually lay carpet on. Under RERA it excludes the external walls and the balcony, and includes internal partition walls.
Built-up areaCarpet area plus the thickness of the walls and the balcony. Typically ten to fifteen per cent above carpet.
Super built-up areaBuilt-up area plus your share of common areas — lobby, staircase, lift, clubhouse, sometimes the gym. Commonly twenty-five to thirty-five per cent above carpet, and occasionally more.

Why RERA changed this

Before the Act, developers were free to quote on super built-up area, and there was no standard definition of what could be loaded into it. Two projects quoting the same rate per square foot could deliver materially different flats. RERA defines carpet area and requires that a property be sold on it, which makes the comparison between two projects meaningful again.

Super built-up has not vanished. It still appears in conversation, in older listings and in resale. What has changed is that the agreement must state carpet area, so the number you sign for is the honest one.

Working out the loading

The loading factor is how much has been added on top of carpet to arrive at the quoted area. If a flat is quoted at 1,000 sq ft super built-up with a carpet area of 700 sq ft, the loading is roughly forty-three per cent of the carpet — or put the other way, you are getting seventy per cent of what you are paying for as usable floor.

The useful move when comparing two projects is to divide the total price by the carpet area rather than the quoted area. A project with a lower headline rate per square foot and heavy loading can work out dearer than one that looks more expensive on the advertisement.

What to check before advising a client

  • Which area the quoted rate refers to — ask explicitly, and get it in writing.
  • The carpet area stated in the draft agreement, not the brochure.
  • Whether the balcony and any enclosed utility area are inside or outside the stated carpet figure.
  • The RERA registration page for the project, which carries the declared areas.

Common questions

What is carpet area as defined under RERA?
The net usable floor area within the walls of the apartment, excluding the external walls and the balcony or verandah, but including the area covered by internal partition walls.
What is a normal loading factor?
Twenty-five to thirty-five per cent above carpet area is the usual range in Mumbai. Higher loading is not automatically unfair, but it should be matched by genuinely better common amenities.
Can a builder still sell on super built-up area?
The agreement must state carpet area under RERA. Super built-up may be mentioned alongside, but it cannot be the basis of the sale.
Is the balcony included in carpet area?
Not under the RERA definition. Balcony and verandah are excluded, which is a common source of confusion when comparing an older listing with a new one.

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