Carpet vs Built-Up vs Super Built-Up: What Are You Really Buying?
When a developer says "1,500 sqft," you typically get 1,050 sqft of walkable space. Convert between all three area types with the correct loading factor for your project — and see the honest ₹/sqft on the space you actually own.
Understanding carpet, built-up and super built-up area
Kolkata buyers routinely lose 25–35% of what they think they're buying to common areas. Here's what the three area terms actually mean, and why RERA changed the game in January 2024.
Carpet area — the real number
The actual usable floor space inside your flat, wall-to-wall — excluding wall thickness, balconies, and any common areas. This is what you can lay tiles on and place furniture in. Post-RERA, this is the legally binding measurement developers must disclose. If you had a party at home, this is the space your guests could stand on.
Built-up area — carpet plus walls
Adds wall thickness and enclosed balconies to the carpet area. Typically 8–12% larger than carpet in Kolkata apartments. A useful reference for interior work quotes but not the number that matters for a purchase decision.
Super built-up area — the marketing number
Built-up area plus your proportionate share of common amenities — corridors, lift lobbies, staircases, clubhouse, gym, swimming pool, security cabin, terrace share. This is the number in most Kolkata developer brochures and cost sheets, because it looks bigger. The gap between super built-up and carpet is called the loading factor.
Loading factor: the number that matters
| Project type | Typical loading | Carpet you actually get |
|---|---|---|
| Older Kolkata apartments (pre-2010) | 18–22% | ~82% of sticker sqft |
| Standard new-launch mid-segment | 28–32% | ~72% of sticker sqft |
| Premium & luxury (big lobbies, clubhouses) | 33–40% | ~65% of sticker sqft |
| Ultra-luxury / bespoke projects | 40%+ | Under 60% of sticker sqft |
Higher loading isn't always a bad thing — it usually means bigger amenities and better common areas. But you must know the number before you sign, because two projects at the same ₹/sqft can differ by 20% on usable space.
The January 2024 RERA shift
Since January 2024, West Bengal property registration is done on carpet area basis (matching central RERA mandates). To avoid revenue loss, the government adjusted circle rates upward — so headline stamp duty percentages didn't change, but the per-sqft valuation of your carpet area is now higher. The takeaway: your legal ownership is defined in carpet, but developer marketing is still mostly super built-up. Always ask for both.
How to negotiate on real numbers
- Ask the developer for the RERA carpet area in writing before Agreement for Sale. This is a legal right under RERA.
- When comparing two projects, always compare carpet ₹/sqft, not super built-up ₹/sqft. It's the only apples-to-apples number.
- If a project has 40%+ loading, verify the amenities justify it — a big clubhouse and pool can, an oversized lobby can't.
- Balcony area is often quoted separately or at a discounted rate — check the cost sheet.
We'll get the exact numbers
Send us the project you're considering — we'll share the RERA carpet area sheet plus the real ₹/sqft on carpet, so you're negotiating on the right number.