Few numbers in Indian real estate cause as much confusion as the area of a flat. A brochure says 1,400 sq ft; the family measures the rooms and finds about 1,000. A neighbour's "same size" flat turns out to be smaller inside. An interior contractor quotes per square foot and the total seems far too high. In each case, the cause is the same: three different areas — carpet, built-up and super built-up — describe the same home, and they differ by hundreds of square feet.
The Real Estate (Regulation and Development) Act, 2016 — RERA — brought a single legal definition of carpet area to new projects across India, and registered projects must now disclose it. But brochures, resale listings, older agreements, society records and casual conversation still use built-up and super built-up figures, and the word "loading" is used in two different ways. For anyone buying, renting, comparing or furnishing a flat, it is worth knowing exactly what each term includes.
This article explains the three areas with dimensioned drawings, sets out the RERA definition of carpet area in plain language, shows how loading is calculated and why the same building can be described as having 30 or 40 per cent loading, and gives a step-by-step method to check a flat's carpet area on site. Loading percentages here are illustrative examples, not norms; actual figures vary by project and must be read from the project's own disclosures. This is general information, not legal advice.
How Indian flats came to have three areas
Independent houses are usually described by plot area and built-up area — the land and the floor area built on it. Apartments are different, because each flat shares land, structure and common spaces with others. As multi-storey housing spread in Indian cities in the late twentieth century, builders began selling flats on a "super built-up" or "saleable" area that added a share of the common spaces — staircases, lift lobbies, corridors, entrance halls and later clubhouses and amenities — to each flat. Because there was no common rule for how much to add, the same usable flat could be marketed at very different sizes, and buyers had no easy way to compare.
Measurement conventions also differed. Older methods, such as the approach in IS 3861 for measuring plinth, carpet and rentable areas, generally measured carpet as the floor area of usable rooms and excluded wall thicknesses, so older documents may show a smaller "carpet" figure for the same flat than a RERA disclosure would. RERA, whose main provisions came into force in 2017, settled the definition for registered projects: carpet area became the legal reference for disclosure and for the agreement for sale. Built-up and super built-up remain in everyday use, but they are descriptive terms whose content depends on who is using them.
| Area term | Is it legally defined? | Typical use | Reliability for comparison |
|---|---|---|---|
| Carpet area (RERA) | Yes — RERA, Section 2(k), for registered projects | Disclosure, agreement for sale, buyer comparison | High — same definition across registered projects |
| Carpet area (older usage) | Varied by convention | Pre-RERA agreements, rentals, resale listings | Medium — check whether internal walls are included |
| Built-up area | No single definition in sales practice | Brochures, resale listings, valuation, some tax records | Medium — wall and balcony treatment varies |
| Super built-up / saleable area | No single definition | Older sales, resale listings, maintenance charges | Low — loading varies widely by project |
| Plot area | Defined by title and survey | Houses, bungalows, land | High for land; not a measure of floor space |
| FSI / FAR built-up area | Defined by local development rules | Approvals: how much may be built on a plot | Not the same as sales built-up area |
Carpet area: the RERA definition
RERA defines carpet area as the net usable floor area of an apartment, excluding the area covered by the external walls, areas under services shafts, exclusive balcony or verandah area and exclusive open terrace area, but including the area covered by the internal partition walls of the apartment. The Act explains that an exclusive balcony or verandah, and an exclusive open terrace, are those appurtenant to the apartment and meant for the exclusive use of the allottee.
In practical terms, carpet area is everything inside the flat's outer walls that the family can use as floor: the living room, bedrooms, kitchen, bathrooms, passages, store and utility rooms if they are inside the external walls, and the footprint of the internal walls between them. It leaves out the thickness of the outer walls, any service shafts or ducts within the flat, and balconies, verandahs and open terraces reserved for the flat, which are disclosed separately. Common areas outside the flat — lobby, stairs, lift, corridor — are never part of carpet area.
Two details are often misunderstood. First, internal partition walls are included in RERA carpet area, so the sum of the room sizes measured wall to wall will be slightly less than the carpet area disclosed; in a typical 2BHK the internal walls may account for roughly 2–4 per cent of the carpet area, depending on wall thickness and layout. Second, a balcony that has been enclosed by a previous owner is still, on paper, a balcony; enclosing it may not be permitted under the building's approvals and society rules, and it does not change the disclosed carpet area.
| Element | RERA carpet area | Built-up area (common usage) | Super built-up area (common usage) |
|---|---|---|---|
| Rooms, kitchen, bathrooms, passages inside the flat | Included | Included | Included |
| Internal partition walls | Included | Included | Included |
| External walls of the flat | Excluded | Included (often full or half of shared walls) | Included |
| Service shafts within the flat | Excluded | Often included | Included |
| Exclusive balcony or verandah | Excluded — disclosed separately | Often included, fully or partly | Included |
| Exclusive open terrace | Excluded — disclosed separately | Varies | Varies |
| Share of lobby, stairs, lifts, corridors | Excluded | Excluded | Included (proportionate share) |
| Share of clubhouse, amenities, entrance areas | Excluded | Excluded | Often included |
Built-up area
Built-up area is the carpet area plus the thickness of the flat's walls, and in common usage also the balcony and sometimes the service shafts and terrace. It is close to the area a flat occupies on the floor plate — what an architect would measure from the outside face of the external walls. Where a wall is shared with a neighbouring flat, some calculations take its full thickness and others half; balconies may be counted fully, partly or not at all. Because there is no single convention in sales practice, a built-up figure is useful only when the document says what it includes.
As a rough guide, walls typically add something like 8–15 per cent to the carpet area of an Indian flat, depending on wall thickness, the number of rooms and the shape of the plan, and balconies add more. A compact flat with many small rooms has proportionally more wall than an open-plan flat of the same size. These are illustrative figures, not standards; the only reliable built-up number is one calculated from the actual drawings.
Built-up area should not be confused with the built-up area used for FSI or FAR calculations in building approvals. Local development control rules define what counts towards permissible floor area — some include balconies or staircases, others exempt them up to limits — and that figure answers a planning question, not a sales one.
Super built-up area and loading
Super built-up area — also called saleable area — adds to the built-up area a proportionate share of the common areas of the building or project: entrance lobbies, staircases, lift wells and lobbies, corridors, common walls and shafts, and often the clubhouse, gym, security cabins, driver's rooms, refuge areas and other amenities. The share is usually allocated in proportion to each flat's size. Because what is counted as common area, and how it is shared, varies from project to project, the same carpet area can appear as quite different super built-up areas.
Loading: two ways of quoting the same thing
Loading is the extra area added on top of carpet area to arrive at super built-up area. It is quoted in two ways, and mixing them up is a common source of argument. The first expresses the extra area as a percentage of carpet area: loading = (super built-up − carpet) ÷ carpet. The second expresses carpet as a share of super built-up, sometimes called efficiency or the carpet-to-saleable ratio: efficiency = carpet ÷ super built-up, and the "loading" quoted is then (super built-up − carpet) ÷ super built-up. For the same flat of 1,000 sq ft carpet and 1,400 sq ft super built-up, the first method gives 40 per cent loading and the second gives about 29 per cent, with an efficiency of about 71 per cent. Both are arithmetically correct; they simply divide by different numbers.
What loading is reasonable depends on the building. A low-rise walk-up building with a single staircase and few amenities has little common area; a high-rise tower with several lifts, wide lobbies, refuge floors, a large clubhouse and landscaped podium has much more. As illustrative examples only, loading on carpet in the range of about 25–45 per cent is often encountered in Indian apartment projects, with lower figures in simple buildings and higher figures in amenity-rich towers. A higher loading is not automatically bad — it may pay for a better lobby, more lifts and real amenities — but it must be known, so that the price per square foot of usable space can be compared.
| Building type (illustrative) | Common area pattern | Loading on carpet — illustrative example | Efficiency (carpet ÷ super built-up) |
|---|---|---|---|
| Low-rise walk-up, 4 flats per floor | One stair, small landings, no lift | ≈ 15–25 % | ≈ 80–87 % |
| Mid-rise with lift, modest amenities | Stair, one or two lifts, corridor | ≈ 25–35 % | ≈ 74–80 % |
| High-rise tower with clubhouse | Multiple lifts, refuge floors, lobbies, amenities | ≈ 35–45 % | ≈ 69–74 % |
| Large township with extensive amenities | Club, sports, landscaped podiums, security | Can exceed 45 % | Below ≈ 69 % |
The percentages in this table are worked examples chosen to show how the two methods relate, not market norms or regulatory limits. The project's RERA disclosure and agreement are the authoritative source for any particular flat.
Price per square foot: the same flat, three prices
Because the area changes, the price per square foot changes with it, even though the flat and the total price stay the same. Take an illustrative flat priced at ₹63 lakh. On a super built-up area of 1,400 sq ft it is ₹4,500 per sq ft; on a built-up area of 1,150 sq ft it is about ₹5,480; on a carpet area of 1,000 sq ft it is ₹6,300. A listing that looks cheaper per square foot may simply be quoting a larger area. Comparing two flats is only fair when both prices are converted to the same basis — and carpet area, being the defined and usable figure, is the right one.
| Area basis (illustrative ₹63 lakh flat) | Area | Price per sq ft | Use this figure for |
|---|---|---|---|
| Carpet area (RERA) | 1,000 sq ft | ₹6,300 | Comparing flats, judging value of usable space |
| Built-up area | ≈ 1,150 sq ft | ≈ ₹5,480 | Understanding the flat's footprint, some valuations |
| Super built-up area | ≈ 1,400 sq ft | ₹4,500 | Reading older listings; only alongside the loading |
| Interiors (always carpet) | 1,000 sq ft | ₹1,200–2,000 mid-range | ≈ ₹12–20 lakh, not ₹16.8–28 lakh on 1,400 |
The same discipline applies to interiors. Interior rates on this site are always per square foot of carpet area — about ₹800–1,200 basic, ₹1,200–2,000 mid-range and ₹2,000–3,500 or more premium in tier-2 cities (indicative October 2026). A quote that applies a carpet-area rate to the super built-up area inflates the total by the loading: for the illustrative flat, a mid-range interior of about ₹12–20 lakh would wrongly become ₹16.8–28 lakh. Maintenance charges, on the other hand, are often levied on super built-up or built-up area by societies; that is a matter of the society's rules, not a measure of the flat's size.
How to check carpet area on site
Carpet area can be checked with a tape or laser meter in an hour. Measure each room, passage, kitchen and bathroom between finished wall faces at floor level, ignoring skirting; multiply length by width; add the rooms together; then add the footprint of the internal walls — their length multiplied by their thickness, typically 100–150 mm for AAC or brick partitions. Exclude balconies, open terraces and service shafts, and measure them separately. Irregular rooms are split into rectangles. The result should be close to the disclosed carpet area, allowing for plaster thickness and measurement tolerance; a gap of more than a few per cent deserves a polite question to the builder or seller.
For the worked flat in Fig. 4, the rooms add up to about 58.7 m², the internal walls to about 2.9 m², and the carpet area to about 61.6 m², or roughly 663 sq ft. If the disclosure for this flat said 660–670 sq ft, the measurement confirms it; if it said 720 sq ft, the difference — nearly 9 per cent — would need an explanation, such as a balcony or shaft having been counted in error.
| Step | What to do | Tool | Common mistake |
|---|---|---|---|
| 1 | Get the RERA-disclosed carpet area and the approved plan for the flat | Project page on the state RERA portal, agreement | Relying on the brochure figure |
| 2 | Measure each room between finished wall faces at floor level | Laser meter or steel tape | Measuring over skirting or furniture |
| 3 | Split L-shaped or irregular rooms into rectangles | Sketch on paper | Treating an L-shape as one rectangle |
| 4 | Add the footprint of internal partition walls | Wall length × thickness | Forgetting walls, then finding the flat 'short' |
| 5 | Measure balconies, terraces and shafts separately | Same tools | Adding them into carpet area |
| 6 | Compare with the disclosure and note any gap | Simple spreadsheet | Ignoring small differences in plaster |
| 7 | Raise significant gaps in writing | Email or letter | Verbal assurances only |
Which area to use, and when
Each area has a proper use. Carpet area is the figure for comparing flats, judging value and pricing interiors, flooring, painting and furniture layouts. Built-up area is useful to understand how much of the floor plate a flat occupies and is sometimes used in valuations. Super built-up area appears in older sale documents, resale listings and society maintenance calculations, and is only meaningful alongside the loading. For a new project registered under RERA, the carpet area in the disclosure and the agreement is the reference. Gujarat buyers will find project details on the Gujarat RERA (GujRERA) portal; every state has its own authority and portal.
| Purpose | Area to use | Why |
|---|---|---|
| Comparing two flats | RERA carpet area | Same definition; reflects usable space |
| Judging price per sq ft | Carpet area | Removes the effect of different loadings |
| Interior, flooring and painting estimates | Carpet area (painting by wall area) | Work happens inside the walls |
| Maintenance charges | As per society rules (often built-up or super built-up) | A society decision, not a measure of size |
| Rent comparisons | Carpet area where known | Listings mix bases; convert before comparing |
| Planning approvals | FSI/FAR built-up as defined by local rules | Different definitions from sales practice |
Where area disclosure is heading
Since RERA, new-project disclosures in India have moved steadily towards carpet area, with balconies and terraces shown separately, and buyers have become far more aware of loading. Online state RERA portals now let anyone see a registered project's approved plans and apartment-wise carpet areas. The remaining confusion lives mostly in resale and rental markets, older documents and casual marketing. As more transactions are made on RERA-registered stock and digital records improve, carpet area is likely to become the default language of Indian housing — which is good for buyers, designers and anyone trying to compare like with like.
Rules for reading flat areas
- Always ask which area a number refers to — carpet, built-up or super built-up — and what it includes.
- Use the RERA carpet area from the project disclosure or agreement as the reference for a new flat.
- Convert every price to a per-sq-ft-of-carpet figure before comparing two flats.
- When loading is quoted, ask whether it is divided by carpet or by super built-up area.
- Check carpet area on site room by room, adding internal walls and excluding balconies and shafts.
- Apply interior, flooring and furniture rates to carpet area only.
- Keep balcony, terrace and parking areas as separate lines; do not mix them into carpet area.
- For legal questions about a specific agreement or dispute, consult a qualified lawyer or the state RERA authority.
Frequently asked questions
What is the difference between carpet area and built-up area?
Carpet area is the usable floor area inside the flat's external walls, including internal walls but excluding external walls, shafts, balconies and terraces. Built-up area adds the thickness of the walls and, in common usage, the balcony, so it is always larger — illustratively by something like 10–20 per cent depending on walls and balconies.
Is the balcony included in carpet area under RERA?
No. RERA excludes exclusive balconies or verandahs and exclusive open terraces from carpet area. They are disclosed separately, and their areas can be added to understand the full space the flat offers.
How do I convert super built-up area to carpet area?
There is no fixed conversion, because loading varies by project. If the loading on carpet is known, carpet = super built-up ÷ (1 + loading); for example, 1,400 ÷ 1.40 = 1,000 sq ft. If efficiency is known, carpet = super built-up × efficiency. The reliable figure is the RERA-disclosed carpet area.
What is a normal loading percentage?
It depends on the building. As illustrative examples, simple low-rise buildings may carry loading of about 15–25 per cent on carpet and amenity-rich towers 35–45 per cent or more. There is no single normal figure; what matters is knowing the loading and comparing price per square foot of carpet area.
Should interior designers quote on carpet area or super built-up area?
On carpet area. All the work happens inside the flat's walls, and a rate applied to super built-up area inflates the total by the loading. Painting is the exception, being priced on paintable wall area.
Sources & standards
- Real Estate (Regulation and Development) Act, 2016 — Section 2(k), definition of carpet area, with the explanations for exclusive balcony or verandah and exclusive open terrace areas
- State RERA rules and portals, including the Gujarat Real Estate Regulatory Authority (GujRERA) — project registration and apartment-wise carpet area disclosures
- Bureau of Indian Standards — IS 3861, Method of measurement of plinth, carpet and rentable areas of buildings
- Bureau of Indian Standards — National Building Code of India 2016, Part 2 (Administration: definitions) and Part 3 (Development Control Rules and General Building Requirements)
- Local development control and building bye-laws — definitions of built-up area and FSI/FAR for planning approvals (vary by city)
- Loading percentages in this article are illustrative worked examples, not norms — read actual figures from each project's disclosures; general information, not legal advice
- Price ranges: indicative October 2026 estimates — confirm locally before budgeting
