How we calculate the estimate

The sources

• Sale prices: median sale value per m² of family dwellings over the last 12 months, April 2025 to March 2026 (INE, Q1 2026), published by parish (NUTS-2024 classification). Where the parish is not published, the municipality applies, and the estimate says so. Where not even the municipality is published, the NUTS III region applies, updated with the median growth of the municipalities in the region, with a wider range and a lower confidence score.
• Rents: median rent per m² of new lease agreements (INE, 2025). These are registered contracts, not adverts, and they read below the rents being signed today: their level is adjusted by a factor measured on real signed contracts. Where the municipality has no published rent, the median for the NUTS III region applies, adjusted to the municipality's price level (the INE sale price of the municipality relative to that of the region), and the estimate says so.
• Bank appraisals: the INE survey of bank appraisals on housing, used as a third source for cross-checking and corrected for its composition bias (it only covers mortgaged properties).
• Number of bedrooms: where INE publishes prices by dwelling type (T0, T1, T2 and so on), we use the area's own ratio; where it does not, we take the scale of the reference city and say that it is borrowed.

Bringing the data up to date

A 12-month median holds for the middle of its window, not the end: read as today's price, it would underestimate any rising market. We update each median with the year-on-year change of the area itself (derived from INE bank appraisals for sales, and from the year-on-year change in INE rents for rents). The part of the window covered by the measurement goes in at full rate; the part between the last publication and today goes in damped, because extrapolating yesterday's full rate would mean pretending to know what has not yet been measured.

From the area's price per m² to the value of the property

Extra areas (terrace, balcony, garden, storeroom) are weighted by their own coefficients, in marginal bands: the first metres of a garden are worth more than the hundredth. The number of bedrooms corrects the price per m² with the scale INE publishes by dwelling type (the ratio between the median for each type and the median for the area), with an adjustment for homes whose size is unusual for their type. For rent, which INE publishes without a breakdown by type, a normalised type index corrects the shape of the scale without changing the level, which always comes from INE. The declared features (condition, floor, light, certificate) adjust within an overall cap: an exceptional property calls for a visit, not for a figure without a safety net.

Furniture counts in the rent and not in the sale value: furniture is not part of the property, a valuer leaves it out and a buyer negotiates it separately, but a tenant pays for it every month. We use the official scale of Portaria n.º 176/2019, which applies to the same INE median rent: plus 3% with an equipped kitchen, plus 6% furnished and equipped.

The result always comes with a range, derived from the sources (age of the data, divergence between sources, size of the adjustment), and a confidence score that drops when the data is borrowed from another level or scarce.

Estimate or bank appraisal?

The Tagus Valor estimate is a statistical estimate, automated and free: official INE medians, adjusted to the property by the coefficients described above. A bank appraisal is something else: a valuer registered with the CMVM visits the property at the bank's request, when there is a mortgage, and signs a report. INE publishes the median of bank appraisals every month, which the estimate uses as one of its sources; a bank appraisal of a specific property can only be carried out by the valuer.

The limits, stated

• An automated estimate cannot see the real state of the walls, the noisy neighbour, the building works next door. A visit by a professional refines the figure on site.
• The values published on the price pages are statistical medians for an area, with the period stated; they are not estimates of specific properties.
• The estimate remains an estimate. It is not a valuation within the meaning of Law 153/2015 and replaces neither a professional visit nor a certified appraisal.

Current reference period for sales data: Q1 2026. Updated quarterly, at INE's pace.