The three definitions
Only one of these is a measure of anything you can stand on. The other two exist for sale pricing and for describing the building, and neither has any place in an interior quotation.
| Term | What it counts | Relative to carpet |
|---|---|---|
| Carpet area | Usable floor inside internal walls, excluding wall thickness | 1.00 |
| Built-up area | Carpet plus internal and external wall thickness, plus balcony | 1.10 – 1.20 |
| Super built-up (saleable) | Built-up plus a share of lobby, lift, staircase, amenities | 1.25 – 1.40 |
| RERA carpet area | Net usable floor, defined statutorily; includes internal partition walls | ≈ 1.00 – 1.03 |
Worked example: one flat, three numbers
Take a genuine Mumbai suburban 2BHK. Everything below describes the same flat, and the same ₹16,20,000 of interior work, differing only in what the rate is divided by.
| Basis | Area | Same ₹16.2 L expressed as | How it reads |
|---|---|---|---|
| Carpet | 720 sq ft | ₹2,250 / sq ft | Premium |
| Built-up | 830 sq ft | ₹1,952 / sq ft | Upper mid |
| Super built-up | 1,010 sq ft | ₹1,604 / sq ft | Mid |
| Super built-up, GST excluded silently | 1,010 sq ft | ₹1,359 / sq ft | Cheap |
Nothing about the scope changed between these four rows. Only the denominator and the tax treatment did.
That last row is the one to watch. A studio quoting ₹1,359 per sq ft on super built-up excluding GST, and a studio quoting ₹2,250 per sq ft on carpet including nothing different, are quoting the identical project. A client comparing the two headline numbers concludes that one is 40% cheaper.
Design and build under one accountable roof
Why three numbers exist at all
The three measures were not invented to confuse buyers, though they are now used that way. Carpet area is the oldest and the simplest: the floor you can lay a carpet on. Built-up area came from construction costing, where the walls are real material that has to be paid for and therefore measured. Super built-up emerged from apartment sale pricing, as a way of distributing the cost of lobbies, staircases, lifts, generators and clubhouses across the flats that use them — which is a legitimate accounting idea, since somebody has to pay for the lift.
The difficulty is that super built-up became the marketing number, and once buyers learned to think in it, every other trade started quoting against it too. RERA addressed this for property sale by requiring carpet area in agreements. Nothing equivalent governs interior quotations, which is why the three numbers still circulate freely in this industry and why the responsibility for insisting on one basis falls on you.
Which basis to use for what
Different trades genuinely measure differently, and that is legitimate. What is not legitimate is mixing the bases within one quotation without saying so.
- Overall project rate: carpet area, always.
- Joinery: running feet, or square feet of shutter face. Never flat area — a wardrobe costs the same whichever flat it goes in.
- False ceiling: square feet of actual ceiling area covered, plus running feet of cove or bulkhead separately.
- Painting: square feet of wall and ceiling surface, which for a typical flat is roughly 3.2 to 3.6 times the carpet area.
- Flooring: square feet of floor laid, plus 5–8% wastage for cutting, stated as a separate line.
- Electrical: per point, not per square foot.
- Civil work: per square foot of the surface actually worked on, or as a capped provisional sum.
Where the difference shows up on site
The area basis is not only a pricing question; it has physical consequences during execution. A studio that priced a false ceiling from a super built-up figure has costed 1,010 square feet of board for a flat with 720 square feet of ceiling, which sounds generous until you realise the reverse error is equally common and lands as a variation. The same applies to flooring quantities, painting quantities and skirting run. Any of these quoted as a multiple of an inflated area will be re-measured at some point, and re-measurement in the middle of a project is always an awkward conversation.
There is one more wrinkle worth knowing. Balconies, dry balconies and enclosed flower beds are inside built-up but outside carpet, and they are also frequently inside the scope of work — flooring, a utility unit, sometimes a small sink. Ask explicitly whether the balcony is inside or outside the quoted area and inside or outside the quoted scope. Those two answers are independent of each other and both need to be written down.
How to establish your real carpet area
- Read the agreementPost-RERA sale agreements state carpet area as defined by the Act. This is your starting figure, not the brochure.
- Measure it yourselfA laser measure costs ₹2,500. Measure each room wall to wall at floor level, multiply, add up. Excluding the balcony and the wall thickness.
- Compare with the builder's drawingDifferences of 2–4% are normal. Differences above 5% are worth raising before your joinery is fabricated.
- Note irregularitiesOut-of-square rooms, projecting columns and beam drops matter more to joinery than the total does. Record them room by room.
- Give the measured figure to every studioOne measured number, issued to all three, removes an entire category of quotation confusion.
Half the quotation disputes we are asked to mediate are not about price at all. They are about what the price was divided by.
Greenbox principal designer
The questions that settle it
Three questions, asked at the first meeting, eliminate this problem permanently. Ask them of every studio, and write the answers down. If the answers are not in the quotation document itself, the quotation is incomplete regardless of how detailed the rest of it looks.
- Which area basis is this rate on? The answer should be 'carpet' and the figure should be on the front page.
- What carpet area figure are you using, and where did it come from? Measured on site, or taken from the agreement, or taken from the brochure — these are three different levels of reliability.
- Is GST inside or outside every number on this document? Not just the total. Some quotations mix the two between sections.
Selected work by Greenbox Design Studio. Tap any image to enlarge.
Frequently asked questions
Which area should interior quotations use?+
Carpet area, measured on site. It is the only one of the three that describes space you can actually build in. A quotation priced on built-up or super built-up area cannot be compared with one priced on carpet without converting it first.
What is the loading factor?+
The ratio between super built-up and carpet area — the share of lobbies, lifts, staircases and amenities loaded onto your flat. In Mumbai it typically runs 1.25 to 1.40, meaning a 1,000 sq ft super built-up flat has 715–800 sq ft of carpet.
Is RERA carpet area the same as usable area?+
Close but not identical. RERA carpet area is the net usable floor area within the internal walls, and it includes the area under internal partition walls while excluding external walls, shafts, balconies and open terraces. It is the most reliable figure you have short of measuring.
How much wall area does a flat have relative to carpet?+
Roughly 3.2 to 3.6 times the carpet area for a standard flat at 9 to 10 foot ceiling height, once both faces of internal walls and the ceiling are counted. This is why painting quantities look surprisingly large against the flat's stated size.
Should I measure my own flat?+
Yes. A laser measure costs about ₹2,500 and an hour of your time gives you a figure you can hand identically to three studios. Builder drawings are commonly 2–4% out on internal dimensions, which is enough to matter when a wardrobe run is fabricated to millimetres.