Floor, usable and weighted area: why the figures differ
A flat’s usable area (užitná plocha) is 69.4 m², its floor area (podlahová plocha) 75.6 m², its weighted area (započitatelná plocha) 73.9 m² — three figures, one flat, one floor plan. None of them is wrong, and each was produced by a different rule. This text shows where those rules diverge, where you will find each figure on record and what goes wrong if you confuse them.
Three figures, one flat, one floor plan
A model 3+kk flat (three rooms plus a kitchenette) in a brick new build (novostavba) in Vinohrady. Let us take the room legend from the floor plan, as the drawing gives it:
- living room with kitchenette — 28.4 m²
- bedroom — 14.2 m²
- room — 11.6 m²
- hall — 6.8 m²
- bathroom — 5.1 m²
- WC — 1.4 m²
- storeroom — 1.9 m²
The total is 69.4 m². Inside the flat there are partition walls (příčka), one load-bearing wall (nosná stěna) and a service shaft; their footprint measures 6.2 m². The flat comes with a balcony (balkon) of 7.2 m² and a cellar storage cage (sklepní kóje) of 3.6 m².
The same inputs produce three results:
- Usable area 69.4 m² — the sum of the rooms; the structures are not measured.
- Floor area 75.6 m² — the sum of the rooms plus the footprint of the structures inside the flat (69.4 + 6.2).
- Weighted area 73.9 m² — usable area plus the balcony at a coefficient of 0.50 and the cellar (sklep) at a coefficient of 0.25 (69.4 + 3.6 + 0.9). Those coefficients come from a model price list, not from the law.
There is 6.2 m² between the smallest and the largest figure. At a model purchase price of CZK 11,900,000, this gives:
- CZK 171,470/m², calculated from the usable area
- CZK 161,028/m², calculated from the weighted area
- CZK 157,407/m², calculated from the floor area
The spread is CZK 14,063/m², i.e. 8.9 %. That is the size of the error you make when you compare two flats by price per metre without knowing which area each seller divided by. And the price of the flat has not changed by a single koruna.
Floor area: the only one defined in legislation
The floor area of a flat in a unit is defined by § 3 of Government Regulation No. 366/2013 Coll. (nařízení vlády). It consists of the floor plan area of all rooms of the flat including the floor plan area of all vertical load-bearing and non-load-bearing structures inside the flat — walls, columns, pillars, chimneys. The area covered by built-in items is also included, i.e. the floor under the bath and under a built-in wardrobe.
Three details that cause disputes in practice:
- Maisonette (mezonet). The staircase is counted only as its lower projection, not on both storeys (podlaží).
- Gallery. It counts as a room only if it has a headroom (podchodná výška) of at least 230 cm.
- Rounding. The result is stated in m² to one decimal place. That is why you will never find 75.63 in an owner’s declaration (prohlášení vlastníka).
Where the figure is recorded: in the owner’s declaration, in the part defining the unit. For each flat it gives the unit number (číslo jednotky), the storey, a list of rooms and the floor area. The declaration is public, and you will find it in the Land Registry’s collection of deeds (sbírka listin). On the extract from the title deed (výpis z listu vlastnictví) for the ownership of a unit, the flat appears in Part B with its unit number and its share in the common parts (podíl na společných částech). Under § 15(3)(c) of Decree No. 357/2013 Coll., the Cadastral Decree (katastrální vyhláška), the Land Registry (katastr nemovitostí) has since 1 January 2024 also recorded the floor area from the deed on the basis of which the unit was registered; for units registered earlier, the cadastral offices (katastrální úřad) are adding it gradually. Where the figure is missing, read the area from the declaration.
This figure is not cosmetic. Under § 1161 of Act No. 89/2012 Coll., the Civil Code (občanský zákoník), the share in the common parts is determined by the ratio of the flat’s floor area to the total floor area of all flats in the building, unless the declaration provides otherwise. The share then determines the weight of the vote at the assembly (shromáždění) and the amount of the contribution to building management (příspěvek na správu domu). An error in the area is therefore carried over into voting rights for the whole time you own the flat.
Usable area of a flat: the advert figure that no legislation defines
It is a plain sum of the room areas without the structures — what you measure when you walk through the flat with a laser measure from wall to wall. No Czech legislation defines it for the transfer of property, and Decree No. 441/2013 Coll., the Valuation Decree (oceňovací vyhláška), does not use the term at all. Even so, it is the most common figure in property adverts (inzerát), because it is the easiest of all to understand: it corresponds to what you can walk on.
Its weakness is that it cannot be verified from a single source. Two adverts with the same figure of 69 m² can mean a flat without a balcony and a flat with the balcony included in the area.
How to tell in two minutes:
- Look for a separate field for the area of the balcony or terrace (terasa). If it is filled in, the main figure probably does not include the balcony.
- Add up the room areas from the legend next to the floor plan in the property particulars (expozé). If the total matches the advertised area, it is the usable area. If the total is lower by the footprint of the structures inside the flat (by 6.2 m² in the model), the advertised area is the floor area under the declaration.
- For a new build, compare the advert with the owner’s declaration. They should differ — but not by more than the footprint of the partition walls.
Weighted area: an agreement, not a standard
Weighted area is not a measurement; it is a calculation. You take the base area and add to it, by means of a coefficient, spaces that are not fully fledged habitable rooms.
In Prague, two sets of coefficients meet:
- Expert valuation (znalecký posudek) under Decree No. 441/2013 Coll., the Valuation Decree: balcony and terrace at a coefficient of 0.17, cellar and attic space at a coefficient of 0.10.
- Developer’s price list (ceník): the coefficients are set by the developer — in our model, balcony 0.50 and cellar 0.25. These coefficients have no basis in legislation. They are a commercial agreement and apply only because someone wrote them into the price list.
In the model, the difference between 0.17 and 0.50 for a 7.2 m² balcony makes a difference of 2.4 m². At a unit price of around CZK 160,000/m², that is roughly CZK 384,000 in what you pay for the balcony — depending on whose coefficient was used.
In the agreement, this has a specific place. The article defining the subject of the transfer must contain the floor area under the owner’s declaration and, separately, the area of the balcony and of the cellar storage cage. A single figure for “total area” without a breakdown is a defect: there is no base to which the contractual tolerance for deviations, and any subsequent additional payment or discount, could relate. What else to check in the future purchase agreement (smlouva o smlouvě budoucí kupní) is discussed in the text on how buying a flat from a developer works.
Balcony, terrace and cellar: why they are not part of the flat’s area
The answer is in § 5(f) of Government Regulation No. 366/2013 Coll.: balconies, loggias (lodžie), terraces and atria are common parts of the building, even if they are accessible only from the flat. In that case they are in the exclusive use of the owner of the unit concerned. Under letter (i), cellar storage cages are also a common part unless they are defined as part of the flat.
Three consequences follow that often come as a surprise:
- You do not own the balcony; you have it in exclusive use. It therefore cannot be part of the flat’s area.
- Repairs to the balcony structure are decided by the assembly and paid from common funds, unless the articles of association (stanovy) provide otherwise. Look for the dividing line between routine maintenance and repairs in the articles, not in the purchase agreement (kupní smlouva).
- Glazing a balcony is an intervention in a common part and in the appearance of the building. It needs the consent of the owners’ association (společenství vlastníků jednotek), not just processing at the building authority (stavební úřad).
There is an exception: the owner’s declaration can define a cellar storage cage as part of the flat. It is then included in the floor area and increases the share in the common parts. You can tell because the cage has the same unit number as the flat in the declaration and is listed among its rooms.
Two more areas of the same flat
Adjusted floor area for property tax
The tax base of property tax (daň z nemovitých věcí) for a unit is the floor area according to the Land Registry, or according to the declaration, multiplied by a coefficient: 1.22 for a unit in a residential building that includes a share in the land, otherwise 1.20. Model flat: 75.6 × 1.22 = 92.2 m². That is the figure that goes into the tax return (daňové přiznání) — not 69.4 and not 75.6.
The return is filed by 31 January of the tax period (zdaňovací období). Whoever bought in 2026 files a return for 2027, i.e. by 31 January 2027; if the Land Registry enters a registration applied for in 2026 only in 2027, the deadline is the end of the third month after the month of entry.
Energy reference area in the certificate
The energy performance certificate (průkaz energetické náročnosti budovy) works with the energy reference area (energeticky vztažná plocha). It is measured from the external dimensions and calculated for the building or a self-contained part of it; the certificate for the building also applies to every flat in it. This gives rise to a widespread misconception: the exemption for buildings with less than 50 m² of energy reference area does not mean that a small flat does not need a certificate. The owner hands the certificate to the buyer or tenant at the latest when the agreement is concluded, and the fine can reach CZK 200,000 for a natural person as well as for a business.
How we handle areas on our own assignments
In the property particulars and in the price list we state three lines separately: the floor area under the owner’s declaration, the sum of the room areas, and the area of the balcony or terrace. We do not add them up into one figure. Next to the floor plan there is a legend with the area of each room, so that readers can do the sum themselves and check us. How we build such a document is described in the text on what the property particulars contain.
This has two drawbacks, and it is only fair to name them. The first: our advert shows a smaller headline figure than a competing advert for a comparable flat, because the competition adds the balcony to the area. In filters and when sorting by price per metre we therefore look more expensive and lose some click-throughs. We accept this knowingly, but it is a real price for accuracy, and it shows on a flat with a large terrace.
The second: if a developer uses its own coefficients in the price list, we do not rewrite them. We state them as they are, including the coefficient values, and add our own three lines. This makes the material longer, and preparation takes two to three days more, because we calculate the figures from the drawings and compare them with the declaration line by line. Anyone who wants the price list quickly does not welcome this delay.
Diagram: what is counted in which area and what is not
SECTION THROUGH A WALL — where the dimension runs
──────────────────────────────────────────────────────────────
outer face inner face
│ │
▼ ▼
┌──────────────────────────┐
│░░░░░░ external wall ░░░░░│ room of the flat
└──────────────────────────┘
│ │
│ └── usable and floor area
│ are measured from here
└── the energy reference area of the
building is measured from here
PARTITION INSIDE THE FLAT — where two areas part ways
──────────────────────────────────────────────────────────────
room A ┌────┐ room B
───────────────│░░░░│───────────────
└────┘
▲
├── usable area: not counted
└── floor area: counted in full
WHAT BELONGS TO WHICH AREA
──────────────────────────────────────────────────────────────
┌─ FLOOR AREA ─────────── § 3 GR 366/2013 ───────── 75.6 m² ──┐
│ │
│ ┌─ USABLE AREA ─── not defined in legislation ─ 69.4 m² ─┐ │
│ │ habitable rooms · kitchen · hall · corridor │ │
│ │ bathroom · WC · storeroom and walk-in wardrobe │ │
│ │ inside the flat │ │
│ │ gallery with headroom from 230 cm │ │
│ │ maisonette staircase — lower projection only │ │
│ └────────────────────────────────────────────────────────┘ │
│ + partition walls and load-bearing walls inside the flat │
│ + columns, pillars, chimneys, service shafts │
│ + floor under the bath and under a built-in wardrobe │
└─────────────────────────────────────────────────────────────┘
OUTSIDE BOTH ─────────────────────────────────────────────────
balcony · loggia · terrace · atrium § 5(f)
cellar storage cage § 5(i)
= common parts, even if accessible only from the flat
exception: a cage defined in the declaration as part
of the flat
┌─ WEIGHTED AREA ── not a measurement, it is a calculation ───┐
│ valuation price list │
│ (model) │
│ base area of the flat ×1.00 ×1.00 │
│ balcony, terrace ×0.17 ×0.50 │
│ cellar storage cage, attic ×0.10 ×0.25 │
│ ───────────────────────────────────────────────────── │
│ model flat 71.0 m² 73.9 m² │
└─────────────────────────────────────────────────────────────┘
TAX AREA ─────────────────────────────────────────────────────
floor area × 1.22 unit in a residential building
that includes a share in the land
floor area × 1.20 other cases
model flat 75.6 × 1.22 = 92.2 m²
Two notes on the diagram. We use 69.4 m² as the base area in both columns so that they are comparable; an expert valuation starts from its own definition of floor area in the annex to the Valuation Decree, so its result may differ by tenths. And the “price list” column is a model: the coefficients are negotiated afresh for each project and are the only place in the diagram without a basis in legislation.
Frequently asked questions
How is the area of a flat calculated? It depends on which area. Floor area under § 3 of Government Regulation No. 366/2013 Coll. is the sum of the floor plans of all rooms, including the partition walls and load-bearing walls inside the flat. Usable area is the same sum without the structures. Weighted area adds the balcony and cellar at an agreed coefficient.
Is the balcony included in the floor area of a flat? No. Under § 5(f) of Government Regulation No. 366/2013 Coll., balconies, loggias, terraces and atria are a common part of the building, even if they are accessible only from the flat. The unit owner has them in exclusive use, but they are not part of the flat.
Why does the owner’s declaration give a different area from the advert? Because the declaration states the floor area including the partition walls, and the advert usually the usable area without them. The difference corresponds to the footprint of the vertical structures inside the flat — 6.2 m² in the model flat.
What is the weighted area of a flat? A commercial conversion, not a measurement. The balcony, terrace or cellar is added to the base area at a coefficient. Decree No. 441/2013 Coll., the Valuation Decree, uses 0.17 for balconies and terraces and 0.10 for cellars; developers’ price lists have their own coefficients, and those are a matter of agreement.
Which area goes into the property tax return? The adjusted floor area: the floor area of the unit multiplied by a coefficient of 1.22 for a unit in a residential building that includes a share in the land, otherwise 1.20.
Key takeaways
The area of a flat is not one figure but at least three, and each of them was produced by a different rule and serves a different purpose. The only one defined in legislation, and the one that decides the share in the common parts, is the floor area under § 3 of Government Regulation No. 366/2013 Coll.; the advert figure is usually the usable area, and the price-list figure tends to be the weighted one. Before comparing two flats by price per metre, it is therefore worth finding out which area that metre came from — for the model flat, it makes a difference of 8.9 %. And for every area figure that appears in an agreement, look in the same article for the sentence on how it was measured.