Listing m² vs cadastre m²: why they don't match, and which number to trust

You see "95 m²" on Idealista, look the flat up in the Catastro and find 103 m², then the cèdula says 81 m². Nobody is necessarily lying. There are three legal ways to measure a Spanish flat, and every document picks its own.

The three measurements

Spain's valuation rules (Orden ECO/805/2003) define them like this, for the whole country (BOE):

Measure	Spanish	What it includes
Useful area	Superficie útil	The floor you can walk on, inside the walls. Excludes interior walls, columns, and ducts over 100 cm²
Built area	Superficie construida	Useful area, plus interior walls, 100% of the façade walls and 50% of the walls shared with neighbours
Built area with common areas	Construida con zonas comunes	Built area, plus the flat's share of the stairs, landings, lobby and so on, by its ownership quota

On the same flat, useful is always the smallest and built-with-common-areas the largest.

Which document uses which

Document	What it shows
Catastro (public lookup)	Built area including a share of common areas. Covered terraces count at 50%, or 100% if closed on three sides. The Catastro says this split is for valuation only (Catastro). It covers all of Spain except the Basque Country and Navarre, which keep their own foral cadastres (Catastro)
Cèdula d'habitabilitat	Only in regions that issue one, such as Catalonia. Useful area, for the flat and for each room (Generalitat)
Escritura / Land Registry	Usually built area, often both. Whatever was declared when the flat was registered
The listing	Whatever the seller or agent chooses. Professionals selling to consumers must have a description with the useful area available (Real Decreto 515/1989, a national rule) (BOE)

The Catastro's number is usually bigger than the space you live in, because it includes your slice of the staircase.

What the difference costs

Barcelona averaged €4.587/m² in 2025, a record (Notariado data via Crónica Global). At that price, 8 m² is worth about €36.700.

A worked example (illustrative numbers):

• Listing: 95 m², €480.000, so it looks like €5.053/m².
• Cèdula: 81 m² useful, so it's really €5.926 per useful m².
• The flat next door lists at €5.300/m² useful. It's the better deal, even though the first flat's number looked lower.

Turn every asking price into price per useful m² before you compare, wherever you buy.

When a gap is a real red flag

• The listing is bigger than the Catastro's built-with-common-areas figure. That's the most generous official measure, so anything above it is marketing.
• The Catastro is much smaller than what you see. This can mean something was added and never declared: an enclosed terrace, an annexed patio, a mezzanine. It may not have a permit. Ask for the licence, and have your lawyer check.
• The escritura and the Catastro disagree by a lot. Fixing the registry is the seller's job before the sale. Small differences have a simpler route than large ones, roughly under or over 10%.

What to do as a buyer

1. Ask the agent which m² the listing uses.
2. Get the useful m². In Catalonia it's on the cèdula, the most honest number. In regions without a cèdula, such as Madrid, ask the seller for it and check the escritura.
3. Look up the Catastro figure, and remember it includes common areas. In the Basque Country and Navarre, use the foral cadastre instead.
4. Compare prices per useful m² across flats.
5. If the listing overstated the size, use it in the negotiation. When the seller or agency sells professionally, art. 3 of RD 515/1989 makes the details in the offer binding, even if the contract doesn't repeat them.