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Carpet area vs built-up area vs super built-up area

Three different ways builders measure the same flat. Only one is the area you can actually use — and only one is legally binding under RERA.

Last updated: 19 May 2026

When you look at a flat brochure that says 1,200 sqft, that number is almost certainly the super built-up area. The actual usable space inside the flat — the carpet area — is usually 25 to 30 percent smaller. So that 1,200 sqft flat might give you a real living area of just 800 to 900 sqft.

Builders quote whichever number sounds biggest. RERA (the Real Estate Regulation and Development Act, 2016) made it mandatory for every sale agreement to state the carpet area, but the marketing material is still allowed to lead with super built-up. So you have to learn the difference.

The three definitions

Carpet area

The net usable floor area inside your flat. Measured wall-to-wall from the inside of the walls. It includes every internal space — living room, bedrooms, kitchen, bathrooms, internal staircase if any, and any internal balcony attached to the flat. It excludes the thickness of the external walls.

This is the area you can actually furnish and live in. RERA Section 2(k) defines it precisely and mandates that this is the area declared in the sale agreement.

Built-up area

Carpet area plusthe area occupied by your flat's walls (internal and external), plus any private balcony or terrace attached to the flat. Typically 10 to 15 percent larger than carpet area.

Super built-up area

Built-up area plusa share of the building's common spaces — lobby, staircase, lift shafts, corridors, building services rooms, and sometimes amenities (clubhouse, gym, pool). The share is called the loading factorand is what builders charge you for under the "super built-up" banner.

A typical loading factor in Indian projects is 25 to 30 percent, but we have seen brochures with 40+ percent loading in luxury projects that include a lot of common amenities. Higher loading is not necessarily bad — you do use those common spaces — but it does mean the per-square-foot price you are paying is buying less of your own flat.

Worked example

Take a brochure that quotes 1,200 sqft at ₹6,000 per sqft. Apparent cost: ₹72 lakh. What does that actually break down to?

  • Super built-up area: 1,200 sqft
  • Loading factor (typical 30%): 277 sqft of common space
  • Built-up area: 923 sqft
  • Wall thickness (~10% of built-up): 92 sqft
  • Carpet area: ~830 sqft

Your effective price per usable square foot is ₹72,00,000 / 830 = ₹8,675 per sqft of carpet, not the ₹6,000 the brochure quoted. The two numbers are 45 percent apart.

What changed with RERA

Before RERA (so, pre-May 2017), there was no standard. Builders in different states used different definitions of "built-up" and "super built-up," and buyers had no legal recourse if the delivered flat was smaller than expected.

RERA changed two things:

  • Standard definition of carpet area — under Section 2(k), it is precisely the net usable floor area inside the walls of the flat. No state-level variation.
  • Mandatory disclosure in the agreement — every registered sale agreement must state the carpet area in unambiguous terms. Builders can still advertise super built-up, but the legal contract is on the carpet area.

If the as-built carpet area is more than 3 percent less than what was promised in the sale agreement, RERA allows the buyer to either withdraw with a full refund plus interest, or claim compensation.

Practical advice for buyers

  • Always ask for the carpet area in writing before you sign anything. Builders are obligated to provide it. If a builder is hesitant, walk away.
  • Compute the effective per-sqft price on carpet area, not on super built-up. This is the right comparison number across projects.
  • Note the loading factor. Two projects with the same super built-up area can have very different carpet areas if one has 25% loading and the other 35%.
  • Visit during construction if possible, after the walls are up. You can measure the room dimensions yourself and confirm the agreement matches reality before final payments.
  • Check the agreement clause on area variance. Many builders include a clause that adjusts the final price if the as-built carpet differs from the agreement carpet — usually they charge you for any excess but only refund for shortfalls beyond some threshold. Read it.

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