When you shop for your first flat, you will hear two area numbers for the same home. One sounds bigger. The bigger one usually sits next to the price per square foot. Knowing how the two relate is the single most useful bit of maths in the whole search.
Two areas, one definition
Carpet area is the space inside your home that you can actually use. Section 2(k) of the Real Estate (Regulation and Development) Act, 2016 (RERA) defines it as the net usable floor area of an apartment. It leaves out the outer walls, service shafts, an exclusive balcony or verandah and an exclusive open terrace. It counts the internal partition walls inside the home. Because the law spells it out, two honest people measuring the same flat should get the same answer.
Super built-up area adds the walls and a slice of the building's shared spaces: lobbies, lift wells, staircases, corridors, service rooms and sometimes the clubhouse. No law defines it. No rule says how the slice is calculated. It is a selling figure, not a measured one.
The gap between the two is called loading.
Working it out yourself
Loading = (super built-up area minus carpet area) divided by carpet area.
| Carpet (sq ft) | Super built-up (sq ft) | Gap (sq ft) | Loading |
|---|---|---|---|
| 650 | 880 | 230 | 0.35 |
| 750 | 1,050 | 300 | 0.40 |
| 900 | 1,215 | 315 | 0.35 |
| 1,100 | 1,540 | 440 | 0.40 |
A loading of 0.40 is often said aloud as "40 per cent". Notice that the first and third rows have the same loading but very different gaps. The ratio alone tells you little until you also look at the carpet area.
The trap: a smaller-sounding number
Some people divide the gap by the super built-up area instead. For the 750 and 1,050 flat, that gives 300 divided by 1,050, about 0.29, instead of 0.40. Same flat, same walls, but it sounds much leaner. If someone quotes you a loading, ask which number they divided by. Better still, ask for both areas and do the sum yourself.
What it does to the price per square foot
Say a flat's total price is ₹72 lakh. On a super built-up area of 1,050 sq ft, that works out to about ₹6,857 per sq ft. On a carpet area of 750 sq ft, it is ₹9,600 per sq ft. The flat and the cheque are identical. Only the divisor changed.
This is why a low rate on a big area can be the same deal as a higher rate on a smaller one. When you compare two homes in your ₹60–90 lakh range, divide each total price by its carpet area. Then you are comparing like with like. Our EMI calculator turns that total into a monthly figure you can hold against your current rent.
Sharing common areas is fair; hiding the method is not
Lifts, stairs, fire refuge areas and pump rooms are real construction, and every home uses them. Someone has to pay for them, so the cost is spread across the flats. That part is reasonable. The problem is only that the seller chooses how to spread it, with no fixed method.
RERA does not set a limit on loading. It does something more useful: it makes carpet area the figure that counts, so the other figure can always be checked against it. Section 12 adds teeth. If you pay money relying on a statement in an advert, brochure or model flat, and that statement turns out to be wrong, the promoter must compensate you. An area figure is exactly that kind of statement, so keep the brochure.
What loading cannot tell you
- Whether the shared spaces are any good. A wide lobby and a second lift raise loading, and you may well want them.
- How usable the home is. Two flats with equal loading can have very different amounts of furnishable floor.
- Anything across projects, unless both quote the same two areas measured the same way.
Questions to ask on your site visit
- What is the carpet area of this exact unit, as it will appear in the agreement for sale?
- What has been counted in the super built-up figure?
- Which area is the rate quoted on?
- Is the balcony inside or outside the carpet area?
- Will the same carpet area appear on the sanctioned plan and in the agreement?
If the answers to the first and last questions do not match, pause before you pay anything. Our first home guide walks through the rest of the paperwork in the order you will meet it.
Step by step: compare two flats in five minutes
- Ask both projects for the carpet area of the exact unit, in writing.
- Ask for the all-in price: base price plus car park, preferential location charges, club charges and any other fixed charges. Leave out GST and registration for now, and add them later for both.
- Divide each all-in price by its carpet area. This is your true rate per square foot of usable space.
- Visit both and pace out the main rooms. Usable shape matters as much as the number.
- Then compare common areas: lifts per floor, lobby width, staircases. These are what the loading pays for.
A worked comparison
Illustrative only. Flat A is quoted at ₹6,500 per sq ft on 1,100 sq ft super built-up, so ₹71.5 lakh, with a carpet area of 780 sq ft. Flat B is quoted at ₹7,200 per sq ft on 1,000 sq ft, so ₹72 lakh, with a carpet area of 800 sq ft. On carpet area, Flat A works out to about ₹9,167 per sq ft and Flat B to ₹9,000. The flat with the higher quoted rate gives you more usable space per rupee.
Common mistakes
- Comparing quoted rates without checking which area they use.
- Forgetting that maintenance is often charged on the bigger area.
- Assuming the brochure area will match the agreement. Check both.
What loading means for your monthly maintenance
Illustrative arithmetic. If maintenance is ₹4 per sq ft per month and charged on 1,050 sq ft super built-up, you pay ₹4,200 a month. If it were charged on the 750 sq ft carpet area, you would pay ₹3,000. That gap of ₹1,200 a month is ₹14,400 a year, every year you live there. So loading affects not just the price, but your running cost too. Ask which area the association will bill on.
A quick checklist to carry
- Carpet area of the unit, in writing
- Super built-up area, in writing
- Which area the rate is quoted on
- Which area maintenance will be charged on
- Balcony and terrace areas listed separately
- Same carpet area in the plan and the agreement
Bring a phone calculator and these six lines. You will understand the deal better than most people in the room.
Words in plain English
- Built-up area: carpet area plus the thickness of the walls and, often, the balcony. Like super built-up, it has no single legal definition.
- Common areas: spaces shared by all homes, such as lobbies, lifts, staircases and corridors.
- Sanctioned plan: the building plan approved by the planning authority.
The short version
Ask for the carpet area, divide the all-in price by it, and compare homes on that number. Then judge the common areas with your own eyes. That is all the maths a first-time buyer needs.