Carpet area to built-up area converter
Enter any one of the four areas and the factors, and the converter returns all of them plus the effective rate per square foot of carpet — which is the number that actually compares two projects. It also converts a pre-RERA MOFA carpet figure to the RERA one.
A pre-RERA agreement usually states the MOFA figure; a post-RERA one states the RERA figure. They describe the same flat.
Loading is a commercial construct, not a defined ratio — it varies by project and there is no standard figure. RERA defines carpet area and requires builders to quote it, so carpet is the only one of these with a statutory meaning. The MOFA figure is what was conventionally quoted before RERA, not a second legal definition.
Built-up area is carpet area plus internal walls and balcony, typically adding 8% to 12%. Super built-up area is carpet area plus a share of common areas, with a loading factor commonly between 20% and 35% but entirely at the developer’s discretion. Only carpet area has a statutory definition under RERA, which — unlike the carpet figure conventionally quoted under MOFA before it — counts the internal partition walls of the flat.
How the calculation works
There is no fixed relationship between the three. Loading is a commercial decision, not a ratio.
The formula: Built-up = Carpet × (1 + loading factor)
A 1,000 sq ft carpet area flat with a 25% loading factor has a super built-up area of 1,250 sq ft. Working backwards, a flat advertised as 1,250 sq ft super built-up at 25% loading has 1,000 sq ft of carpet — which is what you can actually use.
The critical figure the converter derives is the effective rate. A quote of ₹8,000 per square foot on 1,250 super built-up square feet is ₹1,00,00,000, which is ₹10,000 per square foot of carpet area. Two developers quoting ₹8,000 on different loading factors are not quoting the same price, and the effective rate is the only way to see it.
Inputs you will need
Any one of the three areas, plus the wall and balcony allowance and the loading factor. If a developer will not state the loading factor, that is itself informative — it is a number they know precisely.
The quoted rate per square foot, and crucially which area the rate is quoted on. A rate quoted on carpet and a rate quoted on super built-up are not comparable figures, and conflating them is the most common error a buyer makes.
- Any one area. Carpet, built-up or super built-up.
- Wall and balcony allowance. Typically 8% to 12% over carpet.
- Loading factor. Commonly 20% to 35%, but at the developer’s discretion.
- The rate and its basis. Which area it is quoted on.
Worked example: a 1,000 sq ft carpet area flat with 25 per cent loading
Identical usable space, identical headline rate, and a ₹16,00,000 difference in price between the lowest and highest loading.
| Loading factor | Super built-up | Efficiency | Total at ₹8,000/sq ft | Effective rate on carpet |
|---|---|---|---|---|
| 15% | 1,150 sq ft | 87.0% | ₹92,00,000 | ₹9,200 |
| 20% | 1,200 sq ft | 83.3% | ₹96,00,000 | ₹9,600 |
| 25% | 1,250 sq ft | 80.0% | ₹1,00,00,000 | ₹10,000 |
| 30% | 1,300 sq ft | 76.9% | ₹1,04,00,000 | ₹10,400 |
| 35% | 1,350 sq ft | 74.1% | ₹1,08,00,000 | ₹10,800 |
Carpet vs built-up vs super built-up under RERA
The Real Estate (Regulation and Development) Act 2016 defines carpet area as the net usable floor area within the walls of the apartment, excluding the area covered by external walls, shafts, exclusive balcony or verandah and exclusive open terrace, but including the area covered by internal partition walls. Crucially, it requires developers to disclose and sell on carpet area.
That was the central consumer reform in RERA on this point. Before it, developers commonly advertised and priced on super built-up area with the loading factor undisclosed, which made comparison between projects effectively impossible and allowed the same usable flat to be sold at very different real prices.
Built-up and super built-up have no statutory definition and remain commercial constructs. They are not improper to use — a share of common areas is genuinely part of what a buyer acquires — but they are not standardised, and a developer’s super built-up is whatever that developer has decided it is. For maintenance charging, the basis your society uses should be stated explicitly and applied to every flat identically, whichever of the three it is.
- RERA defines carpet area and requires it to be quoted. It is the only one of the three with a statutory meaning.
- Built-up and super built-up are commercial constructs. Not standardised between developers.
- Compute the effective rate on carpet. It is the only comparable figure.
- State your maintenance basis explicitly. And apply it to every flat the same way.
MOFA carpet area vs RERA carpet area
Before RERA, the carpet area a Maharashtra buyer was quoted came from practice under the Maharashtra Ownership Flats Act 1963, which required a promoter to disclose carpet area without defining it the way RERA later did. What was conventionally measured was the floor you could lay a carpet on — the area inside the flat, wall to wall, with the thickness of the internal partition walls left out.
RERA defines it differently. Section 2(k) makes carpet area the net usable floor area excluding external walls, service shafts, exclusive balcony or verandah and exclusive open terrace, but expressly including the area covered by the internal partition walls of the apartment. The walls inside the flat count.
So the same flat carries a larger carpet figure on the RERA basis than on the MOFA one, and the gap is the footprint of its own internal walls. There is no standard percentage for it, because it depends on how the flat is cut up: a studio and a three-bedroom of identical area do not have the same partition footprint. That is why the converter takes it as an input rather than applying a constant.
It matters most at resale and when comparing listings. An agreement executed before RERA and one executed after can state different carpet areas for an identical flat without either being wrong, and a buyer comparing the two figures directly will conclude that one flat is bigger than the other. Convert before you compare. The position is also Maharashtra-specific — other states had their own pre-RERA conventions, and standardising them is part of what RERA did.
- MOFA carpet excluded the internal walls. It was the floor you could lay a carpet on, measured inside the partitions.
- RERA carpet includes them. Section 2(k) expressly counts the internal partition walls of the apartment.
- The gap depends on the layout. More partitions, bigger difference, and no standard figure to apply.
- Convert before comparing listings. A pre-RERA figure and a post-RERA one are not directly comparable.