Method

How the figure is reached

Nothing here is proprietary. A valuation starts from a published average for the area and is adjusted by four factors, each with a stated value. Everything below is the actual arithmetic the tool performs.

published averageper m² or sq ft × type × age × condition × size × area = estimated value

The four factors

Each is a multiplier on the area average. A value of 1.00 leaves the figure untouched. Pick any combination to see what it does.

Type

Age

Condition

The size curve

Smaller homes sell for more per square metre and larger ones for less. The curve is drawn between fixed anchors and read off continuously — an earlier version stepped between brackets, which meant one square metre could move the rate by five per cent.

Drag or hover across the curve.

Two grades of data

The confidence range printed with every valuation is not decorative: it is set by which grade the market falls into.

Registry · ±10%

Austria, France and the United Kingdom. Built from recorded transactions or measured district averages — immopreise.at, Notaires–INSEE and HM Land Registry respectively.

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Survey · ±18%

Every other market. Compiled from published surveys — Global Property Guide, SQMData, the Deloitte Property Index and Redfin — which disagree with one another by roughly 15%. Where no city figure existed, it is interpolated from the country level.

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What it cannot do

It has never seen the property. Floor, aspect, outlook, noise, the state of the roof and what was last done to the kitchen all move a price more than any factor on this page, and none of them are knowable from an address.
Averages hide their own spread. Two flats on the same street can differ by a third. An area average is the middle of a wide distribution, not a prediction for one address.
Survey markets are orientation only. Where the sources disagree by 15%, no amount of arithmetic afterwards recovers the precision.
It is not a valuation. A valuer visits, inspects, and carries professional liability for the number they sign. This is a starting point for that conversation.