Why carpet area and loading factor matter more than the number on the brochure

Three numbers get thrown around when a project is marketed, and they're not interchangeable. Carpet area is the usable floor area inside your walls — the space you can actually put furniture on. Built-up area adds the thickness of your own walls and balconies. Super built-up area goes further and adds a share of common areas: lobbies, staircases, lift shafts, corridors. The number on the brochure and the number on the signboard is almost always the last one, because it's the biggest.

The ratio between super built-up area and carpet area is called the loading factor, and it varies more than most buyers expect — anywhere from roughly 25% to 40% depending on the project's design, amenity load, and how many towers share the common areas. A unit advertised at 1,850 sq ft super built-up with a 30% loading factor gives you about 1,295 sq ft of carpet area. The same advertised size at a 40% loading factor gives you closer to 1,110 sq ft — nearly 200 sq ft less, for the same headline number.

This matters most when you're comparing two projects side by side. A lower price per square foot on super built-up area can still work out more expensive per square foot of carpet area, if that project's loading factor is higher. The only way to compare fairly is to ask both developers for the carpet area and loading factor directly, then do the price-per-carpet-sqft math yourself rather than trusting the headline number.

RERA has helped here — registered projects are required to disclose carpet area, not just super built-up area, in their sale agreements. That's a floor, not a ceiling: the disclosure requirement doesn't stop marketing materials from leading with the larger number, it just means the true figure has to exist somewhere in the paperwork. Ask for it before you sign, not after.

The practical habit worth building: whenever a price is quoted per square foot, ask "per square foot of what?" before comparing it to anything else. It's a five-second question that avoids a comparison that looks fair on a brochure and isn't.