Carpet Area vs Super Built-Up Area: Converting Any Quote in Two Minutes
A builder quotes Rs 9,400 per sq ft. Down the road another quotes Rs 11,000. Most buyers stop there and take the first one, which looks 15% cheaper. Run both through the loading factor and the first flat costs Rs 13,629 per usable square foot while the second costs Rs 12,981 — and the second one has slightly more room in it, for Rs 6.6 lakh less.
That gap is not a trick anyone hides. It is printed in the cost sheet. It is just printed in a unit nobody converts.
Key takeaways
- RERA carpet area is the only legally defined one — Section 2(k) of the Act — and it is what your agreement for sale must state.
- Loading factors run 25% to 40% today, and ran anywhere from 20% to 60% before RERA. There is no legal cap on loading.
- Built-up area is roughly carpet plus 10% to 15%. Super built-up is built-up plus your share of every common area the builder chooses to count.
- The real rate is total price divided by carpet area, and it is the only number worth comparing between two projects.
- Loading costs you twice. Maintenance and property tax are usually billed on super area too, so a 45% loading means 45% more maintenance for the life of the flat.
The three areas, defined properly
Carpet area
Section 2(k) of the Real Estate (Regulation and Development) Act, 2016 defines it as the net usable floor area of an apartment, excluding the area covered by external walls, areas under service shafts, exclusive balcony or verandah area, and exclusive open terrace area — but including the area covered by the internal partition walls of the apartment.
Read that twice, because two clauses surprise people. Internal walls count in. Your exclusive balcony counts out. So a flat with a 90 sq ft balcony has 90 sq ft of usable space that never appears in the carpet figure, and a flat with many small rooms has more internal wall area padding its carpet number than an open-plan unit of the same size.
Built-up area
Carpet plus the thickness of the external walls, plus the balcony and terrace that carpet excluded. It typically comes to carpet plus 10% to 15%. It has no RERA definition, it appears mostly on property tax assessments and older agreements, and it is the least useful of the three for comparing prices.
Super built-up area
Built-up area plus your proportionate share of common areas — lobbies, staircases, lift shafts, corridors, the generator room, the clubhouse, sometimes the podium and the security cabin. What goes into that list is the builder's choice. There is no statutory definition of super built-up area at all, which is precisely why it is the number the rate is quoted on.
Loading factor: the number that decides what you get
Loading is the gap between what you pay for and what you use, expressed against carpet: loading = (super built-up − carpet) ÷ carpet. Here is what different loading levels do to the same 1,500 sq ft super built-up quote.
| Loading | Carpet you get | Space lost vs 25% loading | Rate per carpet sq ft if quoted at Rs 10,000 |
|---|---|---|---|
| 18% | 1,271 sq ft | +71 sq ft | Rs 11,800 |
| 25% | 1,200 sq ft | — | Rs 12,500 |
| 30% | 1,154 sq ft | 46 sq ft | Rs 13,000 |
| 35% | 1,111 sq ft | 89 sq ft | Rs 13,500 |
| 40% | 1,071 sq ft | 129 sq ft | Rs 14,000 |
| 45% | 1,034 sq ft | 166 sq ft | Rs 14,500 |
The swing from 18% to 45% is 237 sq ft — a full bedroom — on identical paperwork at an identical headline rate. High-amenity projects with large clubhouses and multi-level podiums sit at the top of that band. Low-rise and no-frills projects sit at the bottom.
The worked example: the cheaper flat that isn't
| Flat A | Flat B | |
|---|---|---|
| Quoted rate | Rs 9,400 per sq ft | Rs 11,000 per sq ft |
| Super built-up area | 1,650 sq ft | 1,350 sq ft |
| Loading | 45% | 18% |
| RERA carpet area | 1,138 sq ft | 1,144 sq ft |
| Total price | Rs 1.551 crore | Rs 1.485 crore |
| Real rate per carpet sq ft | Rs 13,629 | Rs 12,981 |
| Maintenance at Rs 4.50 per sq ft of super area | Rs 7,425 a month | Rs 6,075 a month |
Flat B has six more square feet of usable space, costs Rs 6.6 lakh less, and saves Rs 1,350 a month in maintenance — about Rs 1.6 lakh over ten years before escalation. Its headline rate is 17% higher. Every buyer who shortlists on rate per sq ft picks Flat A.
This is not hypothetical arithmetic. Two projects in the same sector with different amenity programmes routinely show loading 15 to 25 percentage points apart, and the higher-loading project almost always quotes the lower headline rate. That is the point of quoting on super area.
How to convert any quote in two minutes
- Get the all-in price — basic rate plus preferential location charges, parking, club membership, power backup and IFMS. The cost sheet, not the rate card. Our list of the EDC and IDC charges that get added after the rate covers what to ask for.
- Get the RERA carpet area in writing. It is on the state RERA portal for every registered project, and the developer cannot quote a different figure there than in your agreement.
- Divide. All-in price ÷ carpet area = your real rate. Compare only this number across projects.
- Check the loading separately: (super − carpet) ÷ carpet. Above 40%, ask what you are getting for it, and whether you will use it.
While you are on the portal, pull the floor plan and check that the carpet figure matches the room dimensions. Reading the drawings is a skill worth ten minutes — our guide to what a floor plan, layout plan and master plan each show explains which document answers which question.
What the builder is required to disclose
RERA changed the disclosure, not the pricing practice. A promoter of a registered project must state the carpet area in the agreement for sale and on the authority's portal, and must not sell on any basis other than carpet area. What the Act does not do is stop the marketing rate being quoted on super area — so both numbers appear, and only one of them is used to multiply.
Two protections are worth knowing. If the carpet area delivered is less than what the agreement promised, the model agreement for sale requires the promoter to refund the excess with interest, generally within 45 days. And if the carpet area is more, the promoter can charge only for the increase, at the original rate. Measure the flat at handover rather than after — once you take possession and sign off, the argument gets much harder. Our guide to the possession letter sets out what to check before you sign it.
The cost that follows you for thirty years
Maintenance, sinking fund and in many municipalities the property tax assessment are all calculated on super built-up area. On the Flat A example, the 45% loading adds about Rs 1,350 a month at today's rates. Escalate that at 6% a year and it is roughly Rs 2.1 lakh over ten years and Rs 5.9 lakh over twenty, for common areas you may use twice a month.
None of this argues that loading is illegitimate. Lifts, lobbies, fire staircases and a pump room are real construction that someone has to pay for, and a tower cannot exist without them. The argument is only that you should know the number before you sign, not after. Buyers who want to avoid the question altogether usually end up comparing a flat against an independent floor, where almost nothing is loaded.
FAQ
Does RERA carpet area include the balcony?
No. Section 2(k) specifically excludes an exclusive balcony, verandah or open terrace. Those are usable spaces you are getting outside the carpet figure, which is why two flats with the same carpet area can feel very different.
What is a reasonable loading factor?
25% to 30% for a standard mid-rise or high-rise project. Below 20% usually means limited amenities or a low-rise format. Above 40% means large common areas, a big clubhouse or a podium, and you should decide consciously whether that is worth paying for.
Can a builder change the carpet area after booking?
Only within the tolerance the agreement allows, and any shortfall must be refunded with interest under the model agreement for sale, generally within 45 days. Any increase can be billed only at the original rate.
Which area is used for stamp duty and registration?
Stamp duty is charged on the higher of the transaction value and the circle rate value, and most states apply the circle rate to built-up or super built-up area as defined in their own schedule. It is not calculated on RERA carpet area, which is why the two figures on your paperwork will not agree.
Why do resale listings show a different area than my agreement?
Resale listings almost always quote super built-up area because that is what the original brochure used. Ask the seller for the builder-buyer agreement and read the carpet figure from there before you price the deal.
One last check
Before you shortlist, put every option on one line: all-in price, RERA carpet area, real rate per carpet foot, loading, monthly maintenance. The ranking usually changes. If you would like that table built for the two or three projects you are weighing, send us the cost sheets and we will do the conversion with you.
