The net usable floor area within the internal walls of a unit, excluding the thickness of external walls, shafts, balconies and common areas. Under RERA, carpet area is the disclosure basis for residential sale, defined to exclude external walls and shafts but include internal partition walls.

What is a normal loading factor in India?

Loading varies widely — commonly in the twenties for older or simpler buildings and in the thirties for amenity-heavy developments, but there is no standard and no cap. Because loading is a commercial convention rather than a regulated figure, always compare projects on carpet area and price per carpet square foot.

How do I convert super built-up area to carpet area?

Divide the super built-up area by one plus the loading factor to get built-up area, then divide by one plus the wall factor to get carpet. Both factors must come from the seller's own basis — assuming them produces a number you cannot rely on.

Why is the effective loading higher than the loading I entered?

Because loading is applied to built-up area, not to carpet. With an 8% wall factor and 20% loading, the super built-up is 1.08 × 1.20 = 1.296 times carpet, so the buyer feels 29.6% rather than 20%. The calculator reports the effective figure so the two quotes can be compared honestly.

Carpet area, built-up area and super built-up area calculator

Enter whichever area you actually know and get the other two, with the loading between carpet and the quoted super built-up figure made explicit.

Known area

The area I know isyou enter

Areayou enter

Unityou enter

Factors

Wall and column factoryou enter

Built-up over carpet: internal and external wall thickness, columns and balcony projections.

Common area loadingyou enter

Super built-up over built-up: lobbies, staircases, lifts and shared amenity, as the seller applies it.

Result — calculated from your inputs

Carpet area873 sq ft

Built-up area960 sq ft

Super built-up area1,200 sq ft

Loading

Effective loading, carpet to super built-up37.5%

Carpet as a share of super built-up72.73%

In square metres (carpet)81.08 sq m

Continue to a full site assessment

A calculator answers one question. A DevPartner assessment carries planning capacity, programme, cost, revenue, deal structure and cash flow through one deterministic model and freezes a versioned decision report.

Nothing from this calculator maps into the assessment intake, so you will start from a blank site. No opportunity is created until you save one.

Continue to a full site assessment See a sample decision report

How this calculator works

built-up      = carpet × (1 + wall factor %)
super built-up= built-up × (1 + loading %)

reverse:
carpet = super built-up ÷ (1 + loading %) ÷ (1 + wall factor %)

You enter: A value you supply. Nothing is assumed for you.
Calculated: Arithmetic on your inputs, shown in the working.
Assumption: A factor or allowance you can change — mix ratios, wastage, dry-volume factors.
Approximation: Geometry or method that approximates reality; labelled wherever used.
Verify locally: Planning parameters, statutory rates and structural design must come from the authority or a qualified professional.

The three areas measure different things

Carpet area is the usable floor area within the walls of the unit — what you could actually lay carpet on. Built-up area adds the thickness of walls and columns, and typically balconies and utility areas. Super built-up area adds a share of the building's common spaces: lobbies, staircases, lift shafts, corridors and, in many schemes, amenity blocks.

Only carpet area is defined statutorily for residential sale under RERA, which requires the carpet figure to be disclosed. Loading is a commercial convention with no fixed definition, which is precisely why two projects quoting the same super built-up area can deliver materially different homes.

Loading is the number to interrogate

A loading of twenty percent and a loading of thirty-five percent on the same 1,200 square foot quoted area differ by roughly 130 square feet of usable space. On a per-square-foot price basis, the higher-loaded unit is materially more expensive for the same utility even at an identical headline rate.

Ask what is inside the loading. Lift lobbies and staircases are normal. Clubhouses, swimming pools, basement parking areas and services rooms are sometimes included and sometimes charged separately, and the answer changes the comparison.

Worked example

1,000 sq ft of carpet with an 8% wall factor is 1,080 sq ft built-up. Apply 20% loading and the super built-up quoted is 1,296 sq ft — an effective loading of 29.6% over carpet, not 20%. A buyer comparing a '20% loading' claim against a rival's '25%' is comparing two different bases.

Reverse the calculator to see the same effect: 1,296 sq ft super built-up at those factors returns exactly 1,000 sq ft of carpet.

Mistakes in area basis

Assuming loading compounds on carpet when the seller applies it to built-up, which is the case here and is why effective loading exceeds quoted loading.

Treating balcony, utility and terrace area inconsistently between two quotes.

Using a brochure number instead of the carpet area stated in the agreement, which is the figure that has statutory meaning under RERA.

Limits of this converter

Wall factor and loading are entered by you because they are project-specific and negotiated, not published constants. Change them and every downstream number changes.

The definition of carpet area itself is set by law and by the agreement; this tool converts between bases, it does not decide which spaces count.

Frequently asked questions

What is carpet area?: The net usable floor area within the internal walls of a unit, excluding the thickness of external walls, shafts, balconies and common areas. Under RERA, carpet area is the disclosure basis for residential sale, defined to exclude external walls and shafts but include internal partition walls.
What is a normal loading factor in India?: Loading varies widely — commonly in the twenties for older or simpler buildings and in the thirties for amenity-heavy developments, but there is no standard and no cap. Because loading is a commercial convention rather than a regulated figure, always compare projects on carpet area and price per carpet square foot.
How do I convert super built-up area to carpet area?: Divide the super built-up area by one plus the loading factor to get built-up area, then divide by one plus the wall factor to get carpet. Both factors must come from the seller's own basis — assuming them produces a number you cannot rely on.
Why is the effective loading higher than the loading I entered?: Because loading is applied to built-up area, not to carpet. With an 8% wall factor and 20% loading, the super built-up is 1.08 × 1.20 = 1.296 times carpet, so the buyer feels 29.6% rather than 20%. The calculator reports the effective figure so the two quotes can be compared honestly.