Free calculator · West Bengal
Carpet Area, Built-up Area and Loading Calculator
Turn the area a builder quotes into the carpet area you can actually use, see what you pay for walls and common areas, and compare two flats on price per sq ft of carpet.
Quick answer: Carpet area = super built-up area ÷ (1 + loading). At the 39% Kolkata average loading reported by ANAROCK for Q1 2025, 1,200 sq ft super built-up is about 863 sq ft carpet, so ₹6,000 per sq ft quoted is ₹8,340 per sq ft of carpet.
| Area | Sq ft | Price per sq ft | Share of price |
|---|---|---|---|
| Carpet area | 863.31 | ₹8,340 | ₹51,79,856 |
| Built-up (covered) area | 949.64 | ₹7,582 | ₹56,97,842 |
| Super built-up area | 1,200 | ₹6,000 | ₹72,00,000 |
| Walls (built-up minus carpet) | 86.33 | ₹5,17,986 | |
| Common areas (super built-up minus built-up) | 250.36 | ₹15,02,158 | |
| Everything outside your carpet area | 336.69 | ₹20,20,144 |
Wall share used: 10% (your input). Loading entered: 39% over carpet.
The 39% loading and 10% wall share filled in above are starting points, not facts about your flat. Replace them with your builder's figures. The RERA carpet area should be in the agreement for sale.
Compare two flats
Builders quote different areas and loadings, so the rate per sq ft alone can mislead. Enter each flat as quoted. The calculator converts both to carpet area and tells you which one costs less per sq ft you can use.
| Flat A | Flat B | |
|---|---|---|
| Area quoted (sq ft) | 1,200 | 1,000 |
| Type of area quoted | Super built-up area | Super built-up area |
| Loading over carpet | 39% | 25% |
| Carpet area (sq ft) | 863.31 | 800 |
| Built-up area (sq ft) | 949.64 | 880 |
| Super built-up area (sq ft) | 1,200 | 1,000 |
| Total price | ₹72,00,000 | ₹68,00,000 |
| Price per sq ft of area quoted | ₹6,000 | ₹6,800 |
| Price per sq ft of carpet | ₹8,340 | ₹8,500 |
Loading here is measured over carpet area. Wall share used for built-up area: 10%. A lower price per sq ft of carpet is not the whole story: also compare location, floor, amenities and the builder's record.
Carpet, built-up and super built-up: what each means
- Carpet area is the floor you can use inside the flat. RERA defines it in law (below).
- Built-up area, called covered area by many Kolkata builders, is carpet area plus the thickness of the walls. Some builders also add exclusive balconies here, so ask what is included.
- Super built-up area is built-up area plus your share of common areas such as the lobby, stairs, lift well, corridors and clubhouse. It has no legal definition.
- Loading is how much bigger the super built-up area is than the carpet area.
How it is calculated
With loading measured over carpet area (the default, and the way ANAROCK reports it):
- Loading = (super built-up − carpet) ÷ carpet
- Super built-up = carpet × (1 + loading), so carpet = super built-up ÷ (1 + loading)
- Built-up = carpet × (1 + wall share)
- True price per sq ft of carpet = total price ÷ carpet area
- Paid for common areas = total price × (super built-up − built-up) ÷ super built-up
If your builder adds loading to built-up area, choose "Over built-up": super built-up = built-up × (1 + loading). If the builder says carpet is, say, 70% of super built-up, choose "Share of super" and enter 30. The result always shows the loading over carpet too, so you can compare projects on one basis.
There is no official ratio between built-up and carpet area. Published guides range from 10% to 15% (Shriram Properties) to 15% to 30% (Aditya Birla Capital), so the wall share is your input. The 10% shown is only a starting point.
Worked example
A Kolkata flat is quoted at 1,200 sq ft super built-up for ₹6,000 per sq ft, with 39% loading over carpet and a 10% wall share.
- Total price = 1,200 × ₹6,000 = ₹72,00,000
- Carpet area = 1,200 ÷ 1.39 = 863.31 sq ft
- Built-up area = 863.31 × 1.10 = 949.64 sq ft
- True price per sq ft of carpet = ₹72,00,000 ÷ 863.31 = ₹8,340
- Common areas = 1,200 − 949.64 = 250.36 sq ft, costing 250.36 × ₹6,000 = ₹15,02,158
The RERA carpet area rule in West Bengal
Section 2(k) of the Real Estate (Regulation and Development) Act, 2016 says carpet area "means the net usable floor area of an apartment, excluding the area covered by the external walls, areas under services shafts, exclusive balcony or verandah area and exclusive open terrace area, but includes the area covered by the internal partition walls of the apartment."
West Bengal applies the central Act through the West Bengal Real Estate Regulatory Authority (WBRERA, rera.wb.gov.in). When a project is registered, the promoter must disclose the number, type and carpet area of the flats (Section 4(2)(h)). In January 2026 the West Bengal Real Estate Appellate Tribunal ruled that carpet area means net usable space and a builder cannot use an "engineering tolerance" clause to deliver less (LiveLaw report). No law caps loading.
Sources
- RERA Act 2016, Sections 2(k) and 4(2)(h): India Code. In force for project registration since 1 May 2017.
- Kolkata average loading of 39% in Q1 2025 (30% in 2019): ANAROCK, reported by PTI on 9 June 2025 (The Week).
- WBREAT carpet area ruling, January 2026: LiveLaw.
This calculator converts the figures you enter. It does not measure a flat. For a legal claim about a shortfall, rely on the carpet area in your registered agreement and an independent measurement, and contact WBRERA.
Frequently asked questions
How do I convert covered area to carpet area?
In Kolkata, "covered area" usually means built-up area: carpet area plus the walls. Carpet area = covered area ÷ (1 + wall share). With a 10% wall share, 1,000 sq ft covered is about 909 sq ft carpet. Ask the builder for the RERA carpet area, because the wall share differs between buildings.
What is loading in a flat?
Loading is the extra area added to your flat for walls and common areas such as lobbies, stairs, lift wells and the clubhouse. This calculator measures it the way ANAROCK does: (super built-up area minus carpet area) ÷ carpet area. A 39% loading means you pay for 1.39 sq ft for every 1 sq ft you can use.
What is the average loading in Kolkata?
ANAROCK reported an average loading of 39% in Kolkata in Q1 2025, up from 30% in 2019 (PTI report, 9 June 2025). It varies a lot from project to project, so use the figure for your project.
Must West Bengal builders state the carpet area?
Yes. Under the RERA Act 2016, which WBRERA applies in West Bengal, a promoter must disclose the carpet area of the flats when registering a project (Section 4(2)(h)). Carpet area is defined in Section 2(k). In January 2026 the West Bengal Real Estate Appellate Tribunal held that carpet area means net usable area and cannot be cut down by a "tolerance" clause.
Why do builders define loading differently?
There is no single legal definition of loading or super built-up area. Some builders add loading to carpet area, some to built-up area, and some quote carpet as a share of super built-up. Choose the matching option above, or ask the builder for the carpet area in writing.
Rates and conventions last checked: .