The three numbers, defined
All three describe the same flat. They differ in how much of the building they count.
| Term | What it counts | Defined in law? |
|---|---|---|
| Carpet area | The usable floor inside your flat, including internal partition walls. Excludes external walls, service shafts, the exclusive balcony and the exclusive open terrace. | Yes, in the RERA Act, 2016 |
| Built up area | Carpet area plus the thickness of your walls, plus balcony. Roughly 10% to 15% above carpet. | No statutory definition |
| Super built up area | Built up area plus your proportionate share of common areas: lobbies, corridors, staircases, lift shafts, clubhouse, services. | No statutory definition |
Because the last two have no statutory definition, two developers can compute them differently and both be acting lawfully. That is precisely why the Act anchors the sale to the one number it does define.
What RERA actually requires
The Real Estate (Regulation and Development) Act, 2016 defines carpet area and requires it to be disclosed and used as the basis of sale. The agreement for sale must carry it.
Three practical consequences:
- The agreement is the document that matters. A brochure, a price sheet and a sales conversation can all use a different figure. The agreement must state carpet area.
- You can compare projects honestly. Once you have carpet for two flats, you are comparing like with like for the first time.
- Rate per square foot changes meaning. A rate quoted on super built up looks lower than the same price quoted on carpet. Same money, different denominator.
"Is the size you have quoted me carpet, built up or super built up?" Ask it in writing, early, of every project on your shortlist. Everything in this article is downstream of the answer.
Loading factor: the number nobody prints
Loading is the share added to carpet area to reach super built up. The arithmetic is one line:
Loading factor = (super built up ÷ carpet area) − 1
A flat sold as 1,600 sq ft super built up with 1,150 sq ft carpet: 1,600 ÷ 1,150 = 1.39, so loading is about 39%. Of the 1,600 sq ft you are paying for, 450 sq ft is your share of corridors, lifts, lobbies and the clubhouse.
Typical loading in Indian apartment projects runs roughly 25% to 40%, and it has drifted upward as amenity packages have grown. A project with a large clubhouse, wide corridors and many lifts has more common area to distribute, so it loads more.
So read loading as a description, not a verdict:
- Low loading means more of your money is inside your front door.
- High loading means more of it is in shared space. Whether that is worth it depends entirely on whether you will use that shared space.
If you want to judge the shared space itself rather than just pay for it, the arithmetic of homes per acre and clubhouse area per home is the companion calculation.
Why two flats of the same size differ
Two flats both advertised at 1,700 sq ft super built up can hand you materially different homes:
- Different loading. At 30% loading the carpet is about 1,308 sq ft. At 40% it is about 1,214 sq ft. Nearly 100 sq ft of real living space, invisible in the headline number.
- Different wall thickness. Thinner structural walls put more of the envelope inside the flat. This is one of the quieter arguments for monolithic construction.
- Different efficiency of layout. Carpet area wasted on circulation is still carpet area. A long internal corridor counts, and nobody lives in it.
- Different balcony treatment. Excluded from carpet by definition, but a generous balcony is real usable space. Ask for it as a separate figure.
Reading the sizes published on this site
Every project page on this site publishes configuration sizes as the developer publishes them. For example Capitol Residences lists 3 BHK homes at 1,635 and 1,655 sq ft and a 3.5 BHK at 2,115 sq ft, and Edition lists 3 BHK from 1,136 to 1,406 sq ft with a 4 BHK at 1,866 sq ft.
We publish those sizes exactly as the developer publishes them. The published material does not state which basis each figure uses, so we do not assert that they are carpet, built up or super built up. Ask the project team for the carpet area of the specific unit you are considering, and check that the same number appears in the agreement for sale.
That is not a gap in the project. It is the normal state of Indian residential marketing, and it is exactly why this article exists.
Want the carpet area for a specific unit?
Carpet area, balcony area and the parking allotment sit in the agreement and the approved plan rather than the brochure. The project team can give you all three.
Balconies, terraces and car parks
Three items sit outside carpet area and get treated inconsistently. Pin each one down separately:
- Balcony or verandah. Excluded from carpet area by the RERA definition. Usually stated separately. Ask for the figure, because a 90 sq ft balcony is a usable room in Bengaluru's climate and a 25 sq ft one is a place to stand.
- Open terrace. Excluded from carpet area where it is exclusive to your flat. Relevant mainly on top floors and duplexes, and worth confirming whether it is exclusive or common.
- Car parking. Normally allotted rather than sold as area. Confirm the number of parks, whether they are covered, stack or open, and that the allotment appears in the agreement rather than only in an email.
The questions to ask
- Is the size you quoted carpet, built up or super built up?
- What is the carpet area of this specific unit, in writing?
- What is the balcony area, stated separately?
- What loading factor does that imply? Compute it yourself from the two numbers.
- Does the agreement for sale state the carpet area, and does it match the number you were given?
- How many car parks are allotted, of what type, and where is that recorded?
- What is the rate per square foot on carpet, not on super built up?
Question seven is the one that reframes a shortlist. Converting every project to a rate on carpet area is the only way to compare them on the same basis, and it is the same discipline as comparing configurations by rate rather than ticket price. The carpet figure on the approved plan is also something the RERA filing lets you verify.
What is carpet area?
The net usable floor area within the walls of the flat, excluding the area covered by external walls, service shafts, the exclusive balcony or verandah and the exclusive open terrace, but including the area of internal partition walls. That is the definition in the Real Estate (Regulation and Development) Act, 2016, and it is the only one of the three area terms the Act defines.
What is loading factor and how do I calculate it?
Loading is the share of common area added to your carpet area to arrive at super built up area. Divide the super built up area by the carpet area and subtract one. A 1,600 sq ft super built up flat with 1,150 sq ft carpet has a loading of about 39%. Developers rarely publish it, so you compute it from the two numbers once you have both.
Is a lower loading factor always better?
Not always. Low loading means more of what you pay for is inside your flat. Higher loading can reflect wider corridors, more lifts, bigger lobbies and a larger clubhouse, which are real amenities you may want. Judge it alongside what the common areas actually give you rather than treating a lower number as automatically superior.
Does RERA ban selling on super built up area?
RERA requires carpet area to be disclosed and to be the basis on which a flat is sold, and the agreement for sale must state it. Marketing material may still mention other figures, so read the agreement rather than the brochure, and make sure the carpet number appears there.
Is the balcony included in carpet area?
Under the RERA definition the exclusive balcony or verandah area and the exclusive open terrace area are excluded from carpet area, though they are usually stated separately in the agreement. Ask for the balcony area as its own figure so you know what you are getting.
Does the car park count in the area I am buying?
Car parking is normally allotted separately rather than counted in carpet area. Confirm how many parks come with your unit, whether they are covered, stack or open, and whether they are stated in the agreement, because a park assumed in conversation and absent from the agreement is a common dispute.