MahaRERA Carpet Area: What You Actually Pay For in a Mumbai Flat

A buyer comparing two flats in Chembur was stuck. One was quoted at 1,150 square feet, the other at 1,050 square feet, yet when he stood inside them the smaller sounding flat felt roomier. The puzzle dissolved the moment he asked each sales team a single question: how much of that number is RERA carpet area? The 1,150 figure was a super built-up area padded with a share of lobbies and stairwells, while the 1,050 figure was closer to the real usable space. He had almost paid more for less, misled not by a lie but by two different ways of counting.

The short answer. Carpet area under RERA is the net usable floor area inside your flat, and since RERA a builder must quote and sell on carpet area, not on an inflated super built-up figure. Carpet area excludes external walls, service shafts, and exclusive balconies, but includes your internal partition walls. The trade-off to know: developers may still mention super built-up area in brochures to make a flat sound larger, so always compare flats on their RERA carpet area, check it on the MahaRERA portal, and treat the loading factor as the gap between what you hear and what you can actually use.

What is carpet area under RERA?

Carpet area under RERA is the net usable floor area of your apartment, defined precisely in the law. Section 2(k) of the Real Estate (Regulation and Development) Act, 2016 describes it as the net usable floor area of an apartment, excluding the area covered by the external walls, areas under services shafts, exclusive balcony or verandah area, and exclusive open terrace area, but including the area covered by the internal partition walls of the apartment. In plain terms, it is the space you can lay a carpet on, plus the internal walls that divide your rooms.

This single statutory definition matters because before RERA the word carpet area meant different things to different builders. By fixing one meaning, the law gave every buyer a like for like measure across projects and cities, so a carpet area figure in Chembur means the same as one in Andheri. When a Mumbai developer tells you a flat is a certain carpet area, that number now has a legal definition behind it, and you can hold the developer to it rather than to a vague marketing figure.

How is carpet area different from built-up and super built-up?

The three terms describe ever larger areas, and only one of them is the space you actually live in. Carpet area is the usable floor area inside the flat. Built-up area adds the thickness of the external walls and the balcony to the carpet area. Super built-up area, sometimes called saleable area, adds a share of the building common spaces such as the lobby, staircases, and lift wells on top of the built-up area. Each step outward makes the headline number bigger without adding a single square foot you can furnish.

The table below sets out what each measure includes and whether you effectively pay for it. Understanding the ladder from carpet to super built-up is the difference between comparing flats on what you can use and being dazzled by the largest number on the brochure.

Why must a Mumbai builder sell on carpet area?

A Mumbai builder must sell on carpet area because RERA makes it the required basis for advertising and sale. Under the law that the Maharashtra authority enforces, a promoter can advertise and sell a flat only on the basis of its RERA carpet area, which is why registered projects declare carpet area for each unit type. This ended the old practice of pricing on a padded super built-up figure that could not be independently checked, and it put every buyer on the same footing.

For you, this means the price per square foot that matters is the price per carpet area square foot. A flat that looks cheaper on a super built-up basis can be dearer once you divide the price by the real carpet area, and vice versa. Always ask for the carpet area in writing and reduce every quote to a price per carpet square foot before you compare, because that is the number RERA intends you to rely on. Remember too that registration costs are calculated separately on the agreement value, as our guide to Mumbai stamp duty and the ready reckoner rate explains.

What is the loading factor and how does it inflate the size?

The loading factor is the extra common area a builder adds to your carpet area to arrive at the super built-up figure. If a flat has a carpet area of 1,000 square feet and is sold as 1,300 square feet super built-up, the loading is 300 square feet, or about 30 percent. That loading covers your share of lobbies, staircases, and lifts, which are real and necessary, but it is not private space you can use inside your home.

Loading factors are not fixed by RERA and vary widely between projects, commonly in a range of roughly 25 to 35 percent, and sometimes higher in amenity heavy developments. A higher loading is not automatically bad if the common areas are genuinely valuable, but it does mean you get less private space for the same headline size. The way to see through it is simple: always convert back to carpet area, because two flats with the same super built-up size can differ sharply in what you actually get.

How do you check the carpet area of a project?

You can verify the carpet area of a registered project on the official MahaRERA portal, not just take the sales team word for it. Registered projects declare the carpet area for each unit type in their registration details, so you can cross check the number a builder quotes against the number filed with the regulator. This is one of the most useful, and least used, protections a Mumbai buyer has.

Search the project on the MahaRERA portal, open its registration details, and match the carpet area listed there with what is written in your cost sheet and draft agreement. If the figures do not line up, ask for a written explanation before you pay. Our step by step guide to verifying a project on the MahaRERA portal shows exactly where to look for these declared details.

What if the delivered carpet area differs from the agreement?

If the carpet area you finally receive differs from what your agreement records, the RERA framework provides for an adjustment rather than a silent loss. The standard agreement for sale sets out the carpet area of your flat, and it typically provides that if the final carpet area is more, you pay for the extra, and if it is less, the developer refunds the difference for the shortfall. This keeps the promised size honest through to possession.

Because of this, you should insist that your agreement for sale states the carpet area clearly and explains how any variation will be handled. Keep the declared carpet area, the cost sheet, and the agreement together, and at possession confirm the delivered area against them. If a builder resists putting the carpet area in writing, treat that as a warning rather than a formality, because a number you cannot point to later is a number you cannot enforce.

How do you compare flats fairly on carpet area?

Reduce every flat to the same honest measure before you judge price or size. The checklist below keeps a Mumbai buyer from paying more for a bigger sounding but smaller flat.

1. Ask each builder for the RERA carpet area of the exact unit, in writing.
2. Note the super built-up figure separately and work out the loading factor.
3. Divide the total price by the carpet area to get a true price per square foot.
4. Check the declared carpet area for the unit type on the MahaRERA portal.
5. Match that figure against your cost sheet and draft agreement.
6. Confirm the agreement states the carpet area and how any variation is adjusted.
7. At possession, verify the delivered carpet area against the agreement.

Do this for every shortlisted flat and the comparison becomes fair, because you are measuring homes by the space you can live in rather than by the largest number on a hoarding. The buyer in Chembur ran these numbers, chose the flat with the honest carpet area, and paid for space he could actually use.

Frequently asked questions

What is RERA carpet area in simple terms? RERA carpet area is the net usable floor area inside your flat, the space you can actually use, plus the internal partition walls. It excludes external walls, service shafts, and exclusive balconies. Since RERA, this is the standard, legally defined measure that a builder must use when quoting and selling a home.

Can a builder sell a flat on super built-up area? No. Under RERA a builder must advertise and sell on the basis of carpet area, not super built-up area. Brochures may still mention super built-up figures, but the sale and pricing should be on carpet area. Always ask for the carpet area in writing and compare flats on a price per carpet square foot basis.

What is a loading factor in a flat? The loading factor is the extra common area, such as lobbies and staircases, that a builder adds to your carpet area to reach the super built-up figure. It commonly ranges from about 25 to 35 percent. A higher loading means less private usable space for the same headline size, so always convert back to carpet area.

How can I verify a flat's carpet area in Mumbai? Search the project on the official MahaRERA portal and open its registration details, where the carpet area for each unit type is declared. Match that figure against your cost sheet and draft agreement. If the numbers do not agree, ask the builder for a written explanation before you pay any money.

Last updated 2026-09-06. PropNewz Team.