In May 2026 a buyer comparing two Mira Road flats noticed something odd. Both were advertised at 750 square feet, yet one felt visibly larger when he walked through it. The answer was not in the tiles or the light. One builder was quoting super built-up area and the other the RERA carpet area, and the usable space inside differed by nearly a fifth. Since 2017 the law has settled which number must govern a sale in Maharashtra, and knowing that number is the single clearest way to compare two homes honestly.

The short answer. Under the national real estate law, a developer in Maharashtra must sell a flat and quote its price on the RERA carpet area, the net usable floor area within your walls, not on the larger super built-up figure. The trade off worth knowing is that the carpet area is smaller and less flattering than the super built-up number a brochure loves to show, but it is the only figure that reflects the space you will actually live in, and the only one the law lets a builder be held to.

What exactly is RERA carpet area?

RERA carpet area is the net usable floor area of your apartment, measured within the inner walls. The law defines it as the floor area excluding the space covered by external walls, the areas under service shafts, any exclusive balcony or verandah, and any exclusive open terrace, while including the area covered by the internal partition walls of the flat. In plain terms, it is the space your furniture can sit on plus the thickness of the walls that divide your own rooms. It deliberately leaves out shared corridors, lift lobbies, staircases and the proportionate share of common areas that older sales pitches used to fold into the headline number. Because the definition is fixed in statute, the carpet area of a given flat is the same whichever builder measures it, which is exactly what makes it a fair basis for comparison.

This is the figure that belongs in your agreement for sale. When you see a size on a MahaRERA registered project, the carpet area is the number the developer has committed to, and it is the number you should carry into any comparison between two flats.

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

The three terms describe progressively larger areas, and only the carpet area reflects the space you actually use. Built-up area adds the thickness of the external walls and balconies to the carpet area, so it is larger without adding usable room. Super built-up area, sometimes called saleable area, goes further and loads a proportionate share of common spaces such as lobbies, staircases, the clubhouse and corridors onto your flat. That loading can add anywhere from a quarter to more than a third on top of the carpet area, which is why a flat sold as 1,000 super built-up square feet may offer only around 700 carpet square feet to live in. The table below sets out the terms so you can read any brochure with clear eyes.

The practical lesson is to always ask for the carpet area and to compare flats on that figure alone. A lower loading factor means more of what you pay for is usable space, so two flats at the same super built-up size can differ meaningfully once you look at their carpet areas side by side.

Why must developers sell on carpet area now?

Developers must sell on carpet area because the law made it mandatory to end the confusion that different area definitions once caused. From the time the rules took effect in Maharashtra in 2017, quoting and pricing a flat on the carpet area became compulsory, so that every buyer compares like with like and no builder can inflate a number by choosing a more generous definition. The reform did not shrink any flat. It simply forced the honest number to the front, which means a price per square foot now rests on a consistent, legally defined base. For you the buyer, that is a quiet but powerful protection, because it removes the single most common trick in older property marketing, the silent switch between area definitions from one project to the next. It also means a salesperson who still quotes only a super built-up size is, at best, leading with a figure the law does not treat as the basis of your purchase. When that happens, the right response is simply to ask for the carpet area and to record it in writing, because that is the number your agreement and your price must ultimately rest on.

What happens if the delivered carpet area is different?

If the carpet area you finally receive differs from the area in your agreement, the law provides a settling up rather than leaving you to absorb the change. Where the final carpet area is smaller than promised, the developer is required to refund the proportionate amount you overpaid, together with interest, within the period the rules prescribe. Where it is larger, you pay only the proportionate additional amount, and only within a modest limit. This symmetry matters because it turns the carpet area in your agreement into a real commitment rather than an estimate the builder can quietly revise. Confirm the exact refund timeline and interest treatment under the current rules, since these procedural details are updated from time to time, but hold on to the principle that a shortfall in carpet area is your money to reclaim. Our guide to verifying a project on the MahaRERA portal shows where the committed carpet area is recorded.

How does carpet area affect the price you truly pay?

Carpet area reframes the price per square foot into a figure you can trust, and it interacts directly with your other costs. A flat quoted at a low price per super built-up square foot can be more expensive per carpet square foot than a rival once the loading is stripped out, so the carpet based rate is the one to negotiate on. It also feeds into the government charges, because stamp duty and registration are levied on the value of the flat, and a clear carpet area helps you sanity check that value. Reading the carpet area alongside the full closing cost gives you the true rupee per usable foot, which is the only figure worth comparing across projects. Two flats can carry the same sticker price and the same super built-up size yet differ sharply once you divide by carpet area, and that difference is real money spread across the years you own the home. A buyer who negotiates on the carpet based rate is arguing about the space they will actually use, which is a far stronger footing than haggling over an inflated headline figure. Our explainer on the true cost of stamp duty and registration in Mumbai completes that picture on the charges side.

How do you check carpet area, step by step?

Treat the carpet area check as a routine you run on every flat before you compare prices or pay a booking amount. These steps keep you anchored to the honest number.

1. Ask the developer for the RERA carpet area of the specific flat, in writing.
2. Confirm that same carpet area appears on the MahaRERA registered project record.
3. Ask separately for the super built-up area and work out the loading factor between them.
4. Divide the total price by the carpet area to get the true rate per usable square foot.
5. Compare competing flats on that carpet based rate rather than the headline size.
6. Check the agreement for sale states the carpet area, not a super built-up figure.
7. Confirm the refund and adjustment terms if the delivered carpet area changes.

Run these checks on the actual flat you are weighing. A buyer considering a launch such as Prestige Garden Trails at Mira Road should ask for the carpet area of the exact unit and tower, so the comparison across projects rests on usable space rather than on marketing size.

Frequently asked questions

What is RERA carpet area?

RERA carpet area is the net usable floor area of a flat measured within its walls. It excludes external walls, service shafts, exclusive balconies and open terraces, but includes the internal partition walls of the flat. It is the legally defined figure a developer in Maharashtra must use to sell and price an apartment.

Is carpet area the same as super built-up area?

No. Super built-up area adds a share of common spaces such as lobbies, staircases and the clubhouse onto the flat, so it is much larger than the carpet area. That extra portion, the loading, can add a quarter to more than a third, which is why a flat feels smaller than its super built-up figure suggests.

Do builders in Mumbai have to sell on carpet area?

Yes. Since the real estate rules took effect in Maharashtra in 2017, a developer must quote and price a flat on its RERA carpet area rather than any larger area definition. This ensures every buyer compares flats on the same legally defined basis and no builder can inflate the headline number.

What if my flat is smaller than the carpet area promised?

If the delivered carpet area is smaller than the area in your agreement, the developer must refund the proportionate amount you overpaid, together with interest, within the period the rules prescribe. Confirm the exact timeline and interest under the current rules, but a shortfall in carpet area is money you are entitled to reclaim.

The definitions in this guide reflect the RERA carpet area rules as applied in Maharashtra, summarised in this explainer on how MahaRERA defines carpet area. Because procedural details such as refund timelines are revised from time to time, always confirm the committed carpet area and the current rules on the official MahaRERA portal at maharera.maharashtra.gov.in before you commit.

Last updated 2026-08-13. PropNewz Team.