Area & Measurement
What is Built-Up Area?
The middle number. Bigger than what you can use, smaller than what you're sold — and the one figure with almost no legal weight.
The short answer
Built-up area is your carpet area plus the walls and the balcony. It measures the full footprint your flat occupies on the floor plate — everything inside your front door, including the structure holding it up.
It typically runs 10% to 20% larger than carpet area. It does not include any share of the lobby, lifts, staircase or clubhouse — that step comes next, and it's called super built-up area.
What built-up area includes
Take your carpet area — the usable floor. Now add back the things a carpet cannot cover but that still sit inside your flat:
- Internal walls — the partitions between your rooms
- External walls — the structural envelope, typically counted at 100% for walls you own outright and 50% for walls shared with the neighbouring flat
- Balcony or verandah
- Utility or service area attached to the flat
What it does not include is anything outside your front door. The lift lobby is not yours. The staircase is not yours. The clubhouse is not yours. Those get added at the next stage.
The formula
Built-up area
Built-up area = Carpet area + Wall area + Balcony area
- Carpet area
- 840 sq ft
- Walls (internal + external)
- 110 sq ft
- Balcony
- 60 sq ft
- Built-up area
- 1,010 sq ft
In this example the built-up area is about 20% larger than the carpet area. A ratio of 10–20% is normal. Much beyond that and you should ask why — unusually thick walls, or a very generous balcony, or a definition being stretched.
How it compares to the other area figures
| Term | What it measures | Internal walls | External walls | Balcony | Common areas | Typical size* |
|---|---|---|---|---|---|---|
| Carpet area (literal) | Floor you can lay a carpet on | No | No | No | No | ~810 sq ft |
| RERA carpet area (the legal one) | Net usable floor area per Section 2(k) | Yes | No | No | No | ~840 sq ft |
| Built-up area | Carpet + all walls + balcony | Yes | Yes | Yes | No | ~1,010 sq ft |
| Super built-up area | Built-up + share of lobbies, lifts, stairs, clubhouse | Yes | Yes | Yes | Yes | 1,200 sq ft |
| Saleable area | The number the builder prices against. Usually identical to super built-up. | Yes | Yes | Yes | Yes | 1,200 sq ft |
*On a flat advertised as 1,200 sq ft at a typical 30% loading factor. Actual figures vary by project and must be taken from the RERA-registered agreement, never from a brochure.
Why built-up area exists at all
It is the honest engineering number. If you asked an architect how much of the floor plate your flat occupies, built-up area is the answer. It is what determines how many flats fit on a floor, and it is what a structural engineer thinks about.
What it is not is a consumer-protection number. It tells you nothing about how much of that space you can actually live in, because it counts the walls.
RERA defines carpet area. It does not define built-up area, and it does not require a builder to disclose it.
So built-up area sits in an odd place: too big to tell you what you can use, too small to be what you're priced on. Useful for understanding a floor plan. Useless for comparing two projects.
What to watch for
1. It is sometimes quoted as if it were carpet area
An unscrupulous listing may say "built-up 1,010 sq ft" in a way that implies usable space. It isn't. Roughly 170 of those square feet are wall and balcony. Always ask for the RERA carpet figure.
2. Wall-sharing conventions vary
Walls shared with a neighbouring flat are conventionally counted at 50% for each flat. There is no law compelling this, so it is worth confirming which convention a builder used.
3. It is the wrong number to price against
If you want to compare two projects honestly, divide the total price by the carpet area. Not built-up, and certainly not super built-up. That is the only comparison that means anything.
Frequently asked questions
Is built-up area the same as carpet area?
No. Built-up area is carpet area plus the walls and the balcony — typically 10% to 20% larger. Carpet area is the floor you can actually use; built-up area includes the structure around it.
Is built-up area the same as super built-up area?
No. Super built-up area takes built-up area and adds your share of the common areas — lobbies, staircases, lifts, clubhouse. Super built-up is always the largest of the three figures and is usually what the brochure quotes.
How do I calculate built-up area from carpet area?
Add the wall area and the balcony area to the carpet area. As a rough check, built-up area is usually carpet area plus 10% to 20%. If a builder's figure implies much more than that, ask them to break it down.
Does RERA require builders to disclose built-up area?
No. RERA defines and mandates disclosure of carpet area only. Built-up area has no statutory definition under the Act, which is precisely why it should not be the number you compare projects on.
Is the balcony included in built-up area?
Yes. Unlike carpet area, which excludes exclusive balconies, built-up area includes them. This is one of the main reasons the two figures diverge.