Plinth Area: What It Measures, and What It Does Not

Three area figures follow an apartment from drawing board to registration, and each is measured a different way. Only one of them has a definition in the Act you can hold a promoter to. Plinth area is not that one — but it is the figure the approval, the bye-laws and the tax assessment run on, which is why it appears on documents a buyer eventually has to read.

The definition, and where it comes from

Plinth area is the built-up covered area measured at the floor level of the basement or of any storey. The measurement is taken to the external face of the enclosing walls, so the walls themselves are inside the number rather than outside it.

Two documents settle the method. The National Building Code of India carries the definition used by building bye-laws across the country, and IS 3861, the Indian Standard method of measurement of plinth, carpet and rentable areas of buildings, sets out what is counted and what is not. Neither is a statute in itself; they become binding through the local building bye-laws and the sanctioned plan that adopt them.

What is inside the number and what is outside it

• Counted: the covered area of the floor, including the thickness of the external walls, internal walls, columns and pillars within the covered area.
• Counted separately, floor by floor: each storey has its own plinth area. A building’s total covered area is the sum, not a single figure.
• Not counted: open areas outside the enclosing walls — courtyards, open terraces, uncovered projections, open parking areas and landscaped ground.
• Treated on its own terms: balconies, porches and similar semi-covered spaces, which the method of measurement handles as separate items rather than folding into the plinth figure without qualification.

Plinth area against carpet area against super built-up area

The three figures form a ladder, and the gap between the rungs is where most confusion in a sales conversation lives.

The last row is the important one. Carpet area is defined in the Act; plinth area has a written method of measurement; super built-up area has neither, and the share of common area folded into it is a commercial decision, not a measurement. That is why two projects can quote the same super built-up figure and hand over visibly different homes.

Why plinth area exists at all if you do not buy on it

Because the approvals do. Four things are computed on covered area rather than on carpet area, and all four sit behind the apartment you eventually own.

• Floor area ratio. The permissible built quantum on a plot is expressed as a ratio of covered area to plot area. The sanctioned plan is checked against it in plinth-area terms.
• Building bye-law compliance. Coverage, setbacks and permissible projections are all assessed against the covered footprint.
• Fees and charges levied by the sanctioning authority. Scrutiny and betterment charges are typically assessed on covered area.
• Property tax after possession. The unit-area method used by urban local bodies in Karnataka assesses tax on built-up area, not on carpet area.

So the figure follows the building through its whole official life. It simply is not the figure a sale price is attached to.

How the numbers relate to each other in practice

Carpet area is always smaller than plinth area for the same apartment, because plinth area adds the wall thickness that section 2(k) of the Act excludes. Plinth area is always smaller than super built-up area for the same apartment, because the latter adds a share of space outside the apartment altogether.

The distance between carpet and super built-up is what the trade calls loading, and it is worth understanding as a ratio rather than as a number, which is the subject of its own guide on this site.

Two practical consequences follow. First, a per-square-foot figure is meaningless until you know which of the three areas it is per square foot of. Second, when comparing two homes, compare carpet against carpet — it is the only one of the three whose definition is the same in both cases, because a statute wrote it rather than a marketing department.

Where each figure should appear on paper

An allottee is entitled under section 19(1) of the Act to obtain information relating to the sanctioned plans and layout plans, along with the specifications, as approved by the competent authority. That entitlement is what makes the comparison above possible: you can put the plinth figure on the approved plan next to the carpet figure in the agreement and see whether they describe the same apartment.

Four questions that settle it

• Which area is this figure — carpet, built-up, or super built-up? Ask it every single time a number is quoted.
• What is the carpet area of this exact unit, as it will be written into the agreement?
• May I see the sanctioned plan for this floor, so the covered area can be read off the approval rather than off a brochure?
• If two figures for the same unit disagree, which document governs? The answer should be the agreement and the approved plan, in that order.

These terms, and the documents each belongs to, are collected in the property glossary, and the answers SUYUG gives to the recurring versions of these questions sit on the FAQ page. On the corridor, the configuration-level areas as published for each registered project are listed on the 3 BHK page with the registration each belongs to.