How to find a home's floor area

The quickest way: look the home up here

Search for the address in the box at the top of any page. A home's page shows its floor area in square metres, taken from its latest energy certificate, and the month that certificate's inspection took place. Where the size comes from the certificate for the whole building, or from a close match on the address, the page says so beside the figure.

The price check can do the same for you. Type the asking price and the postcode and leave the floor area empty: it lists the homes in that postcode that have a floor area, and picking one fills it in.

On the energy certificate register

A home in England and Wales needs an energy performance certificate when it is built, sold or let, and the register holds certificates from 2008 onwards. The government's Find an energy certificate service is free: search by postcode, open the certificate for the home and look for the total floor area, given in square metres.

A home can have several certificates from different years. The latest is usually the one to use, unless it was made before an extension or a loft conversion.

What the figure measures

The register defines it as the total enclosed floor area of the property, measured to the internal face of the external walls, following the standards of the Royal Institution of Chartered Surveyors. In other words, the floor inside the outside walls on every storey, counting halls, landings and stairs as well as the rooms.

Why it can differ from a floor plan

An estate agent's floor plan usually gives an approximate gross internal area of its own, and the two figures often differ by a few square metres. The plan may have been drawn at a different time, may include a garage, a conservatory or an outbuilding, and is often marked as approximate. A certificate made before an extension or a loft conversion shows the smaller home.

When the two differ by more than a few square metres, ask the agent which spaces the plan counts. For a price per square metre, use the same kind of figure as the sales you compare with: on this site, that is the certificate's.

When there is no certificate

A home on the market should have one, so ask the agent or the seller. Failing that, measure it: multiply the length by the width of each room, add the halls, landings and stairs, and add up every floor, measuring to the inside of the outside walls. A tape and some care will get within a few square metres, which is close enough to compare prices.

Square feet and square metres

Listings sometimes give the size in square feet. Divide by 10.7639 to get square metres: 1,000 sq ft is about 93 m². The price check takes either; write sq ft after the number.

With a floor area in hand, price per square metre explains what to do with it.