Every apartment sale in India comes wrapped in three different area figures, and it is entirely possible to sign a sale agreement without ever being told which one the price per square foot was based on. Carpet area is the usable floor space inside your own walls — the area you could genuinely lay a carpet across. Built-up area adds the thickness of those walls, plus any attached balcony. Super built-up area, sometimes called saleable area, adds a proportionate share of the building's common spaces: the lobby, the stairwell, the lift shaft, occasionally a clubhouse you may rarely visit.
What RERA actually changed
RERA changed the disclosure rules, not the pricing convention. Since the Act came into force, builders are legally required to state a project's carpet area alongside the sale price. What RERA did not change is the fact that the headline rate — the number quoted in every brochure and every advertisement — is still almost always pegged to super built-up area. Two flats advertised at an identical rate per square foot can hand over meaningfully different amounts of usable space, depending entirely on the loading factor between carpet and super built-up.
Ask for the carpet area in writing before you compare two properties on price — it's the only figure that isn't inflated by shared corridors and lobbies you'll rarely stand in.
That loading factor is not fixed by law. It varies by builder, by project, and sometimes within the same building depending on which wing or floor you're on. A loading of 20% is common; 30% or higher is not unusual in projects with generous shared amenities.
Why it still matters after possession
This matters just as much after possession as it does at the point of sale. Furniture layouts, room proportions, and any renovation budget should all be planned against carpet area, not the number on the brochure — it is the only figure that describes the space you will actually live in.