Carpet area is the floor inside your walls. Super built-up area is what you are billed on: your carpet plus a share of corridors, lobbies, lift cores, staircases and the clubhouse. The ratio between them, called carpet efficiency, tells you how much of what you pay for you can actually use. In a Bengaluru tower it is usually about 75%, so a flat sold as 1,900 sq.ft. has roughly 1,430 sq.ft. you can walk on.
That is why two flats advertised at the same size are rarely the same. You are quoted a flat at 1,901 sq.ft. A friend is quoted 1,901 sq.ft. in a different project. One of you may be getting 150 sq.ft. more floor, and neither advertisement will tell you which.
Carpet area vs super built-up: the three numbers
- Carpet area (RERA). The net usable floor inside your walls. The Real Estate (Regulation and Development) Act, 2016 defines it and developers must disclose it. It includes internal partition walls and excludes external walls, service shafts and your exclusive balcony.
- Carpet plus balcony. What most brochures quote, because it is bigger. Not wrong, but not the same thing.
- Super built up area (SBUA). Your carpet plus a share of the common areas. This is the figure the price is multiplied by.
Worked from real floor plates
All of these are current Assetz homes, taken from the developer's own plans. The first three are at Mizumi Reserve, a tower project at Kudlu. The last two are villaments at Mizu & Ki, off Hennur Road.
| Unit | Super built up | Carpet (RERA + balcony) | Efficiency |
|---|---|---|---|
| 3 BHK apartment, Kudlu | 1,901 sq.ft. | 1,431 sq.ft. | 75.3% |
| 3 BHK large, Kudlu | 2,165 sq.ft. | 1,648 sq.ft. | 76.1% |
| 4 BHK apartment, Kudlu | 2,476 sq.ft. | 1,869 sq.ft. | 75.5% |
| 4 BHK villament with garden, Hennur | 3,070 sq.ft. | 2,463 sq.ft. | 80.2% |
| 4 BHK villament with terrace, Hennur | 3,538 sq.ft. | 2,809 sq.ft. | 79.4% |
The villaments run about five percentage points better. On a 3,000 sq.ft. home that is roughly 150 sq.ft. of extra usable floor, the size of a small bedroom, for the same billed area. Low rise formats usually win here, because there is less shared corridor and lift shaft to divide among the homes. We compare the two projects in full in Mizumi Reserve vs Mizu & Ki.
Where the missing square feet go
Subtract carpet from super built up and you get the common area loaded onto your flat. On the 1,901 sq.ft. Kudlu 3 BHK that is 470 sq.ft. On the 3,070 sq.ft. villament it is 607 sq.ft., which sounds like more until you set it against the size of the home.
Some buyers find a loading factor easier to picture. Divide super built up by carpet. For the Kudlu 3 BHK it is 1.33: for every 100 sq.ft. you live in, you pay for 133. For the villament it is 1.25.
Watch the balcony trick
The same Kudlu unit is quoted two ways in two official documents: 1,305 sq.ft. on the cost sheet (RERA carpet only) and 1,431 sq.ft. in the brochure (carpet plus balcony). Neither is dishonest. But the efficiency changes a lot depending on which you use.
| Unit | RERA carpet | Balcony | Efficiency on RERA carpet | Efficiency with balcony |
|---|---|---|---|---|
| 3 BHK, Kudlu (1,901 sq.ft.) | 1,305 sq.ft. | 126 sq.ft. | 68.6% | 75.3% |
| 4 BHK villament, Hennur (3,070 sq.ft.) | 2,264 sq.ft. | 199 sq.ft. | 73.7% | 80.2% |
If you compare one project's carpet plus balcony against another's RERA carpet, you will reach the wrong answer. Always ask which basis a number uses, and compare like with like.
Price per carpet foot
Take the cost sheet total and divide by carpet rather than super built up. On that Kudlu 3 BHK, ₹2,56,55,031 divided by 1,431 sq.ft. is about ₹17,900 per usable square foot. On RERA carpet alone, 1,305 sq.ft., it is about ₹19,700. The hoarding says ₹10,700.
That number is uncomfortable, which is exactly why it is worth working out. It is also the only figure that lets you compare a high efficiency villament against a lower efficiency tower honestly. Our guide to reading a Bangalore cost sheet shows where that ₹2.57 crore total comes from.
What to check before you compare two flats
- Carpet area as per RERA, and separately the balcony area.
- Super built up area for the same unit.
- The efficiency percentage. Ask the sales team to state it.
- The floor plate with room dimensions, not a rendered image.
- That the sale agreement states the RERA carpet area, since that is the figure the law protects.
Any project confident in its planning will hand these over without hesitation. Hesitation is itself the answer.
