The number in a listing is not the floor you will walk on. As the official texts stood on 5 November 2026, the Planned Areas Zoning Regulation defines brüt alan as the area inside the flat's outer contour, while net alan is the space between the walls; a construction portal estimated in May 2026 that gross with common-area shares is 1.20–1.35 times net. Before you sign, have both brüt and net written into the contract, because, as the same portal warns, a bare 'm²' leaves open which area was meant.
What brüt and net actually measure
Under the Planned Areas Zoning Regulation, brüt alan means the area enclosed by the independent section's outer contour, not the floor you can furnish. Shafts, light wells, ventilation ducts and gallery voids stay out of that figure. On every side except the façade, the contour runs along the centre axis of the wall, so a shared wall is split between two flats. Annexes such as a storeroom are recorded separately and must be stated apart.
Net alan is the floor between the walls, including rooms that connect inside the flat, but excluding voids within it. That is closer to what you pace out with a tape measure.
Genel brüt alan goes further: it takes the flat's total gross area and adds the share of the building's common areas that falls to that flat. This is the widest of the three measures, and a figure that simply says "m²" may mean any one of them.
How much floor the advertised number gives you
A construction portal's estimate, as of 12 May 2026, puts gross area with common-area shares at 1.20 to 1.35 times net. That is the conversion to run in your head: a flat marketed as 100 m² gross gives roughly 75 to 83 m² of usable floor. The range is the portal's estimate, and the exact ratio for a given flat has to be checked.
One news outlet reported on 25 February 2026 that a flat advertised as 100 m² can come out as low as 75 m² once the real measurement is made. That is the lower end of the portal's range, and it shows the gap is not a rounding error. When you see a figure in an advertisement, do not assume it tells you which area was measured, and expect the space you can actually furnish to be smaller. The exact difference cannot be read from the listing alone; before you rely on it, have both brüt and net written into the contract.
What sellers sometimes fold into the square footage
The car park, the lift shaft, the stair landings and the building's shelter are not living space. But one news outlet reported on 25 February 2026 that some sellers and agents divide these common areas up and add them to a flat's square footage. The practice makes the advertised figure look larger than the floor the buyer will actually use, because the extra area belongs to the building as a whole rather than to any one flat.
The same newspaper reported on 25 February 2026 that valuation reports then show a notably smaller area than the listing. Comparing the listing figure with a valuation report is one way to spot the gap before you rely on the advertised size.
Check the flat's construction area and land share in the approved project
Under articles 12(a) and 16 of the Condominium Law, the approved architectural project records each independent section's construction area and its arsa payı, the share of the land attached to it. The land share is calculated in proportion to the section's value, taking account of its location and size. That means two flats with the same advertised square footage can carry different land shares, because the share follows each section's value, which depends on its location and size.
Owners hold the building's common areas in proportion to those land shares, not according to the square footage shown in an advertisement. The approved project is therefore the document where the flat's construction area and its stake in the building are set down. When you compare what a seller says with what the project records, you are checking the figures that the law uses, rather than the number chosen for marketing.
What to write into the contract before you sign
A construction portal's professional recommendation, dated 12 May 2026, is blunt: write both brüt and net into the contract. If the document says only 'm²', which area was meant stays open to argument later — one party can read it as the figure on the listing, the other as the smaller floor between the walls. Having both numbers on the same page removes that ambiguity, and it costs nothing to add a second figure next to the first.
Consumer guidance from the Ministry of Trade, checked in May 2026, advises the same check from the buyer's side: go through the flat's gross and net areas and compare them with what the contract records.
Put it simply: a contract with only one area figure is a contract with a question mark. The portal's advice, which the Ministry of Trade's consumer guidance (checked in May 2026) echoes, is that the answer should already be on the page.