Calculate the square footage (and square meters) of any rectangular space.
Area = length × width, shown in both square feet and square meters.
When buying an apartment in India, "square footage" isn't one number — RERA (the Real Estate Regulation Act) legally defines three, and builders have historically priced on the largest one. Carpet area is the actual usable floor space inside your walls, the area a carpet could physically cover, excluding the wall thickness itself. Built-up area adds the thickness of your own walls plus balconies, and typically runs 10–20% larger than carpet area. Super built-up area — the figure many builders quote and price against — adds a further share of common areas: lobbies, staircases, lifts, clubhouse and other shared amenities. Carpet area is usually only around 70% of built-up area, and roughly 70–80% of super built-up area, though the exact ratio (called the "loading factor") varies by project and can run 25–60% above carpet area.
Since RERA came into force, builders are legally required to quote and sell based on carpet area, not super built-up area — a real and useful protection, but it means a "1,000 sq ft" listing from a pre-RERA project and a "1,000 sq ft" RERA-compliant listing can represent genuinely different amounts of usable space. Always ask explicitly which of the three figures a price or listing refers to before comparing two properties, and if a builder quotes super built-up area, ask for the loading factor so you can back-calculate the actual carpet area you're paying for.
Carpet area is the net usable floor space inside your unit's walls — the area a wall-to-wall carpet could physically cover — excluding the thickness of your own walls, balconies, and any shared spaces. It's the smallest and most honest of the three area figures, and the one RERA requires builders to quote.
Built-up area typically runs 10–20% larger than carpet area, because it adds the thickness of your unit's own internal and external walls plus any balcony or verandah area, none of which count as usable carpet space.
Built-up area covers only your own unit (walls, balcony, usable space). Super built-up area — sometimes called "saleable area" — adds a proportional share of the building's common areas: lobbies, staircases, lifts, corridors, and shared amenities like a clubhouse. It's always the largest of the three figures, and historically the one builders priced against before RERA.
Before RERA, builders could advertise and price by super built-up area, which inflates the apparent size (and reduces the effective per-sq-ft price) without buyers always realising how much of that figure was shared common space rather than their own usable area. RERA now requires carpet area to be the basis for pricing and disclosure, making it easier to compare listings on a like-for-like basis.