Carpet Area vs Built-up vs Super Built-up Area: What RERA Says, and What You Actually Pay For

In short: the RERA Act defines only one area: carpet area, the usable floor inside your flat. Built-up and super built-up area are trade terms that add walls and a share of common areas on top. When you compare flats, compare the price per square foot of carpet area, and make sure the agreement for sale states the carpet area.

Carpet area: the only one defined by law

Section 2(k) of the Real Estate (Regulation and Development) Act, 2016 defines carpet area as the net usable floor area of an apartment. It:

• includes the area covered by internal partition walls inside the flat;
• excludes the external walls, service shafts, and any exclusive balcony, verandah or open terrace.

The Act explains that an "exclusive" balcony, verandah or open terrace is one attached to your flat for your use only. Those spaces are not part of carpet area, but the Act still requires them to be declared, as below.

Built-up and super built-up area: trade terms

The RERA Act does not define built-up or super built-up area. They are terms builders and banks use, and the exact make-up can differ between projects. As ICICI Bank explains them:

The extra share added for common areas is often called the loading or loading factor: super built-up area = carpet area × (1 + loading). Two flats with the same super built-up area can have quite different carpet areas if their loading differs.

Common areas themselves are defined in section 2(n) of the Act. They include the land of the project, staircases, lifts and their lobbies, fire escapes, common entrances and exits, common basements and terraces, parks, play areas, open parking and common storage. In a flat, you also get an undivided share of the land: see our guide to UDS.

What RERA requires the builder to disclose

• Carpet area of every unit. When registering a project, the promoter must state the number, type and carpet area of the apartments for sale, along with the area of any exclusive balcony, verandah or open terrace attached to each (section 4(2)(h)). You can see these details on the project's TNRERA page: here's how to check a project's TNRERA registration.
• A registered agreement before a large advance. A promoter cannot take more than 10% of the cost of the apartment as an advance or application fee without first signing and registering a written agreement for sale (section 13(1)).
• No changes to the plan without your consent. The promoter cannot make additions or alterations to the sanctioned plans, layout plans and specifications of your apartment without your prior consent (section 14(2)).
• Penalties. A promoter who breaks provisions of the Act (other than sections 3 and 4) can be fined up to 5% of the estimated cost of the project (section 61).

Some state regulators have gone further in their own orders. Uttar Pradesh RERA directed developers in January 2024 to sell apartments on carpet area only, and Haryana RERA (Gurugram) said in 2021 that sale on super area was illegal. Each state's regulator decides its own directions, so in Tamil Nadu check the TNRERA project page and the agreement itself.

Work out the real price per square foot

Brochures often quote a rate per square foot of super built-up area. To compare flats fairly, convert it to carpet area. An example with illustrative numbers:

In this example the loading is 30% (1,040 ÷ 800 = 1.3), so every square foot you can actually use costs ₹9,100, not ₹7,000. Run the same sum for each flat you're considering. Then add the other charges, such as car parking, club membership, GST, stamp duty and registration: our hidden costs guide lists them. Need to convert between square feet, square metres or grounds? Use our area unit converter.

Checklist before you book

• Get the carpet area in writing, separately from balcony and terrace areas, and match it with the project's TNRERA page.
• Ask for the loading in percentage terms, and what common areas it covers.
• Compare flats on price per carpet sq ft, not on the brochure rate.
• Read the agreement for sale before paying more than 10%: check how the price is worked out and what happens if the final carpet area differs.
• At handover, measure the flat or have it measured, and compare it with the agreement.