See the difference between estimating carpet area from a built-up area and measuring usable floor space directly. Animated floor plans show both approaches and their limits.
Open the carpet area calculator · More Physics and Math videos
The calculation
Estimated carpet area = built-up area × assumed fraction
Worked example
With an assumed 70% share, 1,000 ft² × 0.70 = 700 ft². Changing the assumption to 65% or 75% changes the estimate to 650 or 750 ft². Separately, two measured rectangular spaces of 5 × 4 m and 3 × 2 m total 26 m².
A 70% ratio is an assumption, not a universal definition. Establish which walls and spaces belong in the area under the applicable definition; a floor-covering purchase can require a different measurement.
Video chapters
- 0:00 — Does 1,000 ft² mean 1,000 ft² usable?
- 0:12 — 70% is an assumption
- 0:27 — 1,000 × 0.70 = 700 ft²
- 0:42 — Change the assumption, change the answer
- 0:57 — Measure actual shapes when you can
- 1:13 — Match the measurement definition
- 1:32 — Reverse-check the estimate
- 1:46 — Label estimates; verify measured area
Read the full transcript
A property is described as one thousand square feet of built-up area. Does that mean one thousand square feet of carpet area? Not necessarily. The answer depends on which spaces the area definition includes, and on the actual building layout.
A quick estimate sometimes uses seventy percent of built-up area. Picture the whole area divided into one hundred equal squares. Under that assumption, seventy squares belong to the estimated carpet area. This is a shortcut, not a universal building rule.
Convert seventy percent into decimal form by dividing by one hundred. That gives zero point seven. Multiply one thousand square feet by zero point seven. The estimate is seven hundred square feet, with three hundred square feet outside the assumed share.
Keep the same one-thousand-square-foot total, but compare sixty-five percent and seventy-five percent. Those assumptions give six hundred fifty and seven hundred fifty square feet. The hundred-square-foot spread comes entirely from the assumed ratio, not from a changed building.
For a direct geometric measurement, split the relevant floor area into rectangles. A room five meters by four meters has twenty square meters. A second room three meters by two meters adds six. Together those two measured rectangles contain twenty-six square meters.
Check the definition before adding spaces. For example, India's RERA definition includes internal partition walls, while excluding external walls and specified balcony and terrace areas. The measured surface for fitting carpet is a different question. Do not use one area label for several incompatible totals.
Check the percentage example by reversing it. Seven hundred divided by zero point seven returns one thousand square feet. That confirms the arithmetic under the seventy-percent assumption. It does not confirm a property's surveyed area, or the amount of flooring to order.
For a quick estimate, multiply built-up area by an explicitly stated fraction. For an actual area, use measurements and the applicable definition. Keep the same area units throughout. Our seven-hundred-square-foot answer is an estimate based on seventy percent, not a measured guarantee.