Built-up Area Calculator

Calculate gross built-up area (BUA) and plinth footprint from RERA net carpet area, balcony cantilevers, and exterior/interior wall thicknesses. Supports 2D blueprint schematics and PDF export.

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How to Use Built-up Area Calculator

  1. Select your preferred measurement units (Square Feet, Square Meters, or Square Yards) and pick a predefined layout (1 BHK, 2 BHK, 3 BHK, Duplex Villa) or start from scratch.
  2. Choose a Wall Construction preset (Standard Brick, AAC Blocks, Mivan Aluform RCC, or Custom) to configure exterior perimeter and interior partition wall thicknesses.
  3. Add or adjust rooms with custom dimensions (Width × Length) and classify them as Carpet Area, Balconies, Utility Yards, or Terraces.
  4. Configure municipal compliance factors (100% or 50% balcony inclusion) and multi-floor multipliers for multi-storey duplexes or apartment blocks.
  5. Review the live 2D architectural blueprint schematic, floor efficiency rating, structural material estimates (cement, steel, bricks), and export the schedule as a professional PDF certificate or CSV report.

Architectural Principles of Built-up & Plinth Area Measurement

In accordance with IS 3861:2002 (Method of Measurement of Plinth, Carpet and Rentable Areas of Buildings) and the Real Estate (Regulation and Development) Act (RERA) 2016, Built-up Area represents the total covered floor area measured up to the outer finished face of exterior walls at the plinth level. Where walls are shared between adjoining tenements (party walls), half the wall thickness is apportioned to each unit. Key components of Built-up Area include: 1. Net Usable Carpet Area across all habitable and sanitary spaces. 2. Thickness of internal non-structural partition walls. 3. Full thickness of external envelope and load-bearing walls. 4. Cantilevered and recessed balconies, verandahs, and service utility yards. 5. Air conditioning ledges, plumbing pipe ducts, and electrical shafts located within the plinth boundary.

Carpet vs. Built-up vs. Super Built-up Comparison Matrix

• Carpet Area: 100% usable room footprint inside walls (Living, Bed, Kitchen, Bathrooms, internal passages). • Built-up Area: Carpet Area + 10%–18% (External & Internal Walls + Balconies + Service ducts). • Super Built-up Area: Built-up Area + 20%–35% Developer Common Loading (Lift shafts, grand lobbies, stairwells, security gates, transformer rooms). Understanding these ratios prevents real estate buyer deception and ensures precise civil quantity takeoff during structural foundation and brickwork estimation.

Frequently Asked Questions

What is the difference between Carpet Area and Built-up Area (BUA)?
Carpet Area (RERA Net Usable Area) is the physical space within the inner walls of an apartment that can be covered by a carpet. Built-up Area (or Plinth Area) equals the Carpet Area PLUS the area occupied by interior partition walls, exterior perimeter envelope walls, private balconies, and utility wash yards.
What is the standard formula to calculate Built-up Area?
Built-up Area (BUA) = Net Carpet Area + Total Internal Partition Wall Area + Exterior Envelope Wall Area + Balconies & Verandahs + Service Shafts/Ducts within Plinth. Typically, Built-up Area is 10% to 20% larger than the net usable carpet area.
How do wall thicknesses affect Built-up Area?
Exterior perimeter walls are typically 9 inches (230 mm) for standard brickwork or 8 inches (200 mm) for AAC blocks, accounting for 7% to 12% of the floor footprint. Interior partition walls are usually 4.5 inches (115 mm) or 4 inches (100 mm), contributing another 3% to 6% of the carpet footprint. Modern Mivan shear walls (160mm exterior / 100mm interior) provide higher spatial efficiency.
Are balconies included in Built-up Area under Indian RERA and municipal bylaws?
Under RERA, private balconies and exclusive terraces are excluded from the 'Carpet Area' definition but are fully part of the 'Built-up Area'. Some municipal corporations (such as BMC Mumbai or BBMP Bengaluru) offer 50% FSI concessions on open cantilevered balconies, while others compute 100% of the covered projection.
What is a healthy Floor Efficiency Index (FEI)?
Floor Efficiency Index (Carpet Area ÷ Built-up Area × 100) measures how efficiently a floor plan utilizes structural space. A rating above 82% is considered excellent architectural efficiency, 78%–82% is standard for residential apartments, and below 75% indicates heavy structural or spatial loading.