ESTIMATION

Carpet Area

Net usable floor area within walls; the RERA-mandated sale basis

Also calledusable areanet floor arearera carpet area
Related on InfraLens
CODES
IS 3861
Definition

Carpet area is the net usable floor area of an apartment — literally the area where a carpet could be laid — measured within the inner faces of the unit's walls. Under the Real Estate (Regulation and Development) Act 2016 (RERA), it explicitly includes the internal partition walls of the unit but excludes the external walls, service shafts, exclusive balcony/verandah and exclusive open terrace area (which are reported separately), and all common areas.

RERA made carpet area the only legal basis for selling residential property in India, ending the earlier opaque 'super built-up' practice. Carpet area is typically 65-75% of the super built-up area depending on the loading factor the developer applies for common amenities. IS 3861 standardises the method of measurement of plinth, carpet and rentable areas for buildings.

Where used
  • RERA-compliant sale agreements + price quoting (₹/sq ft of carpet)
  • Stamp duty + registration valuation
  • Property tax assessment by ULBs
  • Comparing real estate offers across developers
  • Interior fit-out + flooring quantity estimation
Acceptance / threshold
RERA Sec 2(k): carpet area = net usable floor area excluding external walls, areas under services shafts, exclusive balcony/verandah and exclusive open terrace, but including internal partition walls of the apartment.
Frequently asked
What is the difference between carpet area and built-up area?
Carpet area is the usable area within walls. Built-up area adds the thickness of the unit's walls and balconies (≈ carpet area + 10-15%). Super built-up area further adds a share of common areas (lobby, stairs, lift).
Is carpet area mandatory under RERA?
Yes. RERA 2016 requires every residential sale to be quoted and agreed on carpet area only. Developers can no longer sell on super built-up area, making price comparison transparent.
Related terms
Built-up Area
Carpet area plus wall thickness + balconies (≈ plinth area of the unit)
Abstract Estimate
Cost estimate at concept stage based on plinth area or per-bed/per-room rates. ±20% accuracy.
Quantity Estimation
Estimate cement, steel, sand, aggregate for given area
Detailed Estimate
Quantity-based estimate from drawings. Each work item × unit rate × quantity = cost. ±5% accuracy.
Contingency
Provision for unforeseen costs. CPWD: 3%. Private: 5-10%. Higher for renovation than new build.
Bill of Quantities (BOQ)
Itemised list of work activities with quantities and unit rates — forms the priced contract document.
Rate Analysis
Computation of unit rate from material + labour + plant + overhead + profit. Reference: DSR, state SOR, in-house DB.
Construction Cost Estimation
Per sqft cost ₹1500-3500 in India
Material Wastage Factors
Cement 2-3%, steel 3-5%, tiles 5-10% typical
FSI / FAR (Floor Space Index)
Ratio of total built-up floor area to plot area; the master density control