Convert carpet area to built-up and super built-up area using wall and common-area allowances.
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Carpet, Built-up and Super Built-up Area Calculator: Free Online Tool
The Carpet, Built-up and Super Built-up Area Calculator converts the usable carpet area of a flat into its built-up and super built-up areas. You enter the carpet area, the percentage allowed for walls and structure, and the percentage allowed for common areas. The result shows all three areas in square feet and square metres, plus the share of the super built-up area that you can actually use.
Home buyers, real estate agents, architects and students use this tool because the same apartment can be advertised using different area definitions. Prices are often quoted per square foot of super built-up area, so understanding the difference between what you pay for and what you can use is important when you compare projects.
When to use this calculator
Use this calculator when you compare apartment offers from different developers, check a sale agreement, or estimate the price per usable square foot. It helps buyers see how much of the quoted area is common space such as lobbies, stairs and lifts. Architects and estimators can use it to test planning efficiency in early layouts, and students can use it to learn the area terms used in property documents. Because both allowances are editable, you can match the loading practice of a specific project and see how the result changes.
How to use the Carpet, Built-up and Super Built-up Area Calculator
- Open the calculator above on your phone, tablet or computer. Nothing needs to be installed and no sign-up is required.
- Choose the unit system first (feet / inches or metres / mm). The input labels change to match your choice.
- Enter your values in the input boxes: Area unit, Carpet area (sq ft), Walls and structure (% of carpet), Common area loading (% of built-up). The boxes already hold sample values, so overwrite them with your own.
- Press Calculate. The result appears straight away under the button.
- Change any value and press Calculate again to compare options. Press Reset to go back to the sample values.
- Check the result against your drawings, project specification and local code before you order material or approve work.
How the calculation works
The calculator works in two steps. First, built-up area is carpet area x (1 + walls percentage / 100). The default walls and structure allowance is 15 percent of the carpet area. Second, super built-up area is built-up area x (1 + common area loading / 100). The default common area loading is 25 percent of the built-up area. For the default carpet area of 800 sq ft this gives a built-up area of 920 sq ft and a super built-up area of 1,150 sq ft. The efficiency figure is carpet area divided by super built-up area, which is 69.6 percent by default. You can enter the area in square feet or square metres.
Worked example
When you open the page the calculator is filled with sample values. Pressing Calculate with those values gives the result below, which you can use to check that you are reading the output correctly.
| Areas | |
|---|---|
| Carpet area | 800.00 sq ft (74.32 m²) |
| Built-up area | 920.00 sq ft (85.47 m²) |
| Super built-up area | 1,150.00 sq ft (106.84 m²) |
| Carpet area / super built-up | 69.6 % |
Tips and common mistakes
- Allowances differ by project and by city, so ask the developer for the exact wall and loading percentages instead of relying on the defaults.
- Compare apartments on carpet area and price per carpet square foot as well, not only on the super built-up rate that is advertised.
- Make sure you select the right area unit. Entering a value in square metres while square feet is selected gives a result that is about ten times too small.
- Common area loading is applied to built-up area, not to carpet area. Use the correct base when you try to match a developer's figure.
- Treat the result as an estimate. Final areas come from the approved plan and the sale agreement, so verify them against those documents.
Frequently asked questions
What is carpet area?
Carpet area is the usable floor area inside the walls of a flat, where you could lay a carpet. It does not include the thickness of the walls. It is the starting input of this calculator.
What is built-up area?
Built-up area is carpet area plus the area taken by walls and structure. In this calculator it is carpet area increased by the wall percentage, which is 15 percent by default.
What is super built-up area?
Super built-up area is built-up area plus a share of common spaces such as the lobby, stairs and lift. Here it is built-up area increased by the common area loading, 25 percent by default.
What does the efficiency percentage mean?
It is carpet area divided by super built-up area. With the defaults it is 69.6 percent, meaning about 70 percent of the area you pay for is usable floor space inside the flat.
Are the default percentages fixed rules?
No. They are editable starting values. The calculator note says allowances differ by project. Use the figures stated in your project documents or agreement to get a result that matches your case.
Important note
This tool gives estimates for planning, study and quick checks. It does not replace design by a qualified engineer, site-specific testing, or the requirements of your project specification and local building code. Always confirm final quantities, test results and acceptance limits with the responsible engineer before using them for construction or payment.
