Property area: the official register area and the area measured from the map

Tonttikartta shows a property's area computed from its parcels' map boundaries. It is not the official area recorded in the property register. Usually the two figures are close, but not always. This guide explains where differences come from and where to get the official figure.

The official area is in the property register

The property register records, among other things, each register unit's area (Real Property Register Act section 7). According to the National Land Survey, a register extract gives the total area and, separately, the land and water areas.

The register area is not always exact either. The National Land Survey notes it can be inaccurate, especially when it rests on an old survey. The register keeper may refine or change location and area data on reliable evidence (section 8).

How Tonttikartta computes the area

Tonttikartta computes the area from the boundaries of all of a property's palstas on the National Land Survey's open cadastral index map. The official register area is not part of the open data, so it cannot be shown.

The computed area tells you how large an area the boundaries on the map enclose.

Why the figures can differ

Map boundaries are as accurate as their boundary markers were measured. On old boundaries the position can be off by metres, and that shows in the area.
The register area may have been set from an old survey that has not been refined since.
Water: the register states land and water area separately, while an area computed from the map boundary does not separate them.
Shares in common areas, such as jointly owned waters, belong to the property but are register units of their own and do not appear as the property's palstas.

A difference alone therefore does not show that either figure is wrong. A large difference is, however, a reason to check the boundaries and the register data.

Where to get the official area

The official area is on the property register extract, available from the National Land Survey. Extracts are charged for; current prices are on the National Land Survey's website. The cadastral survey documents give more detail on boundaries and area.

Area in a property sale

Under the Land Code a property has a defect in quality when, among other things, the seller gave the buyer incorrect or misleading information about its area before the sale. Where area matters in a sale, agree which source the stated area rests on and check it against the register extract.

Law and sources

English translations of Finnish laws in Finlex are unofficial; the Finnish and Swedish texts are authoritative.

This guide is general information, not legal advice. Legal effects are decided by the authorities and the documents named in it; the links open the current consolidated law in Finlex.

Checked against the sources in October 2026

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