Carpet, built-up, super built-up: the only definition that matters
RERA fixed the definition of carpet area. Here is how to read a quote so you are comparing like with like.
Before RERA, "super built-up" meant whatever a developer wanted it to mean. A 1,000 sq ft quote could deliver 620 sq ft of usable floor. RERA now requires carpet area to be stated: the net usable area within the walls, excluding the external walls, shafts, balcony and terrace — though balcony and terrace areas are disclosed separately.
Built-up adds the thickness of internal walls. Super built-up adds a proportionate share of lobbies, staircases, lifts and amenities — the "loading". Loading of 30–40% is common in Mumbai; above that, ask why.
When comparing two properties, convert both to carpet and divide the price by that number. A ₹4 crore flat at 1,200 sq ft super built-up with 40% loading is 720 carpet — ₹55,555 per carpet sq ft. Another at ₹4.2 crore and 900 carpet is ₹46,666. The cheaper headline is the more expensive property.
Every listing on this site quotes carpet area and price per carpet square foot for exactly this reason.