Carpet Area vs Built-Up Area under RERA: A 2026 Mumbai Buyer Guide

A buyer comparing two BHK flats in Mulund in September 2026 almost picked the one advertised as 1,050 square feet over another listed at 720, until she asked one question: which number is the carpet area? The 1,050 figure was super built-up, and the actual RERA carpet area was the same 720 square feet as the other flat. The two homes were nearly identical in usable space, but one had dressed up its number with a 31 percent loading factor. Knowing which area you are being sold is the difference between comparing flats fairly and being quietly overcharged for air.

The short answer. RERA carpet area is the net usable floor area inside your flat, and since the Real Estate Regulation Act took effect, builders must sell and price on carpet area, not on super built-up area. Built-up area is carpet plus wall thickness and balcony, typically 10 to 15 percent more than carpet, and super built-up adds a share of common areas such as lifts and lobbies, usually 25 to 35 percent more through what is called the loading factor. The trade off to internalise is simple: always compare flats on carpet area, because a larger super built-up number can hide a smaller home. Verify the registered carpet area on the MahaRERA portal before you book.

What is RERA carpet area, exactly?

RERA carpet area is the net usable floor area of your apartment, defined in law. Under Section 2 of the Real Estate Regulation Act, it is the net usable floor area, excluding the area covered by external walls, the areas under service shafts, and any exclusive balcony, verandah or open terrace, but including the area covered by the internal partition walls of the apartment. In plain terms, it is the floor you can actually lay a carpet on, plus the internal walls that divide your rooms. This is the number that matters, because it is what you will live in, and after RERA it is the number the builder is legally required to quote. When a brochure gives you only a super built-up figure, you are not yet looking at the size of your home. A useful habit is to translate every flat you see into a single carpet number in your head. Furniture, tiling, painting and the sense of whether a room feels cramped all track carpet area, not the marketing figure, so a 720 square foot carpet flat will feel the same whether the brochure calls it 720 or dresses it up as 1,050. Once you fix on carpet area as your yardstick, most of the confusion in a sales pitch simply falls away.

How does built-up area differ from carpet area?

Built-up area is your carpet area plus the space taken by walls, balcony and any service ducts that fall within your unit. It is typically 10 to 15 percent larger than the carpet area, and it represents the physical footprint of your apartment including its own walls, rather than just the usable floor inside them. Built-up area is a genuine measure of your unit, but it is not what you use day to day, and it is not the RERA sale basis. If a seller quotes built-up area, treat it as a bridge figure and ask for the carpet area underneath it, because a price that looks reasonable per built-up square foot can look very different once converted to the usable carpet you are really paying for.

What is super built-up area and the loading factor?

Super built-up area is your built-up area plus a proportionate share of the building's common areas, such as staircases, lifts, lobbies and amenities. The gap between the super built-up figure and your carpet area, expressed as a percentage of carpet, is the loading factor, and a loading of 25 to 35 percent is normal in Indian apartments. A higher loading is not automatically bad, since grand lobbies and rich amenities have to be paid for by someone, but it does mean that two flats with the same super built-up number can have very different usable space. The loading factor is where a lot of buyer confusion lives, so always ask for both numbers and compute the loading yourself rather than accepting a headline area at face value. The arithmetic is easy: divide the super built-up figure by the carpet figure, subtract one, and the result is the loading. If a flat quotes 940 super built-up on 720 carpet, that is a loading of about 31 percent. Running this one calculation on every shortlisted flat lets you see instantly which projects are quoting honestly and which are leaning on a generous loading to make a modest home look large.

Why does RERA force builders to sell on carpet area?

Because before RERA, buyers routinely paid for space they could never use. In the pre RERA years, marketing was built around super built-up area, so a buyer could pay for 1,000 square feet and receive a home with 700 square feet of usable floor, with the difference explained away as common area loading. The Real Estate Regulation Act ended that by requiring sale and pricing on the RERA carpet area, which gives every buyer a like for like basis to compare projects. This is one of the clearest buyer protections the law introduced, and it is why you should insist on the carpet area figure in the agreement, not just in conversation. If a developer is quoting you super built-up as the sale area, that is a signal to slow down and ask questions.

How do I check the carpet area before I buy?

Verify it against the project's registration on the MahaRERA portal, not just the brochure. Every registered project in Maharashtra has a MahaRERA page that lists the approved details, and the sale agreement must state the carpet area. Match the carpet area in the brochure, the agreement and the RERA registration, and question any difference. While you are on the portal, it is worth confirming the project is registered at all and reading its filings, which we cover in our companion guides. Once you are satisfied with the area, budget for the registration cost using our note on Maharashtra stamp duty and registration charges, and check completion status through our guide to the partial occupancy certificate, since a part complete building can affect what you actually take possession of.

What if the delivered carpet area is less than promised?

You have a defined remedy, because carpet area is a RERA protected term. If the carpet area handed over is smaller than what the agreement records, that is a shortfall you can raise, and MahaRERA provides a complaint mechanism for exactly this kind of dispute. The agreement is your anchor, so the carpet area must be written into it in square feet or square metres, not left to a vague super built-up description. Measure or have the delivered flat measured against the agreement figure at possession, and if there is a genuine gap, take it up through the MahaRERA process rather than accepting an informal explanation. This is precisely why insisting on the carpet number in writing at booking matters so much later. A promise made in a showroom carries no weight at possession, but a carpet area written into a registered agreement is something a regulator can hold the builder to.

What should I verify before booking?

Run this list before you pay a booking amount.

1. Ask for the RERA carpet area in square feet, and refuse to compare flats on super built-up alone.
2. Ask for the super built-up figure too, and compute the loading factor yourself.
3. Confirm the project and its carpet area on the MahaRERA portal against the brochure.
4. Check that the sale agreement states the carpet area explicitly in writing.
5. Compare the per carpet square foot price across the shortlisted projects.
6. Treat a loading factor well above 35 percent as a question to raise, not a detail to ignore.
7. Keep the brochure, the agreement and the RERA page together so any mismatch is easy to spot.

Frequently asked questions

What is RERA carpet area? RERA carpet area is the net usable floor area of an apartment, excluding external walls, service shafts and exclusive balconies or terraces, but including internal partition walls. It is defined in the Real Estate Regulation Act and is the figure builders must use to sell and price a home, so it is the number you should compare across projects.

What is the difference between carpet area and super built-up area? Carpet area is the usable floor inside your flat. Super built-up area adds the walls, balcony and a share of common areas such as lifts and lobbies, and is usually 25 to 35 percent larger. The gap is the loading factor. Two flats with the same super built-up number can have very different usable carpet area.

Can a builder sell a flat on super built-up area? No. Under RERA, builders must sell and price residential apartments on the RERA carpet area, not on super built-up area. If you are being quoted only a super built-up figure as the sale area, ask for the carpet area and make sure it is stated in the sale agreement before you book.

What can I do if the carpet area is less than promised? The carpet area must be stated in your sale agreement, and if the delivered area is smaller, you can raise a shortfall complaint through MahaRERA. Measure the delivered flat against the agreement figure at possession, and pursue any genuine gap through the official MahaRERA process rather than accepting an informal explanation.

Last updated 2026-09-14. PropNewz Team.