Is this a formal valuation?

No. It is an estimate computed from official public data. HM Land Registry sold prices, the UK House Price Index and the EPC register. A formal valuation is a RICS surveyor inspecting the actual property.

Why is your figure different from an estate agent’s?

An agent’s appraisal is a pitch to win your instruction, and it typically sits at or above the honest range. Our figure is built from what nearby homes actually sold for.

What can’t your data see?

Condition, interiors, extensions that never triggered a certificate, and anything that has not sold or been certificated since records began. Interior condition alone can move a price by around 20%, which is one reason the range exists, and why you can tell us what you know.

Methodology

How our house valuations work

Every valuation site gives you a number. Almost none will tell you how it was made. Here is our method, end to end (the data, the maths, and the limits) because a figure you can audit is worth more than a figure that flatters you.

The evidence ladder

We use the strongest evidence each property actually has, and fall back honestly, never to an invented number. In order:

1 · The same kind of home, nearest first

We start where a local agent would: recent sales of the same type of home (a flat is never evidence for a house, and new builds sell at a premium so they are left out) in your postcode, then the rest of your street, then the neighbouring postcodes, then the wider district. Every sale is moved to today by the official index for its own property type. The closer and more recent a sale, the more it counts, and each ring is weighed by how much evidence it holds, so one unusual sale on your road nudges the figure rather than setting it.

2 · This home’s own sale, carried forward

A previous sale of the same home is the strongest single fact there is, because it already reflects the size, condition and position no dataset can see. We carry it forward on the official index and blend it with the neighbourhood evidence. A sale from last year counts for a lot, one from twenty years ago for much less. A recorded “sale” that looks nothing like a normal sale of the whole home (a garage, a part-share, a family transfer) is left out. If the Land Registry record is missing your sale, you can tell us what you paid, always labelled as your figure, never dressed up as a registry fact.

3 · Size, when it is on record

Tell us your home’s floor area and we size the estimate to it, using the going rate per square metre of nearby homes whose floor area is on the EPC register. Many homes have no energy certificate, so we never guess a size: without one, the estimate rests on the same-type sales around it.

4 · Brought up to this month

Land Registry data trails the market: sales register weeks after completion and the newest index month is first published on a fraction of its eventual sales. We bridge that last leg with the Nationwide index (built at mortgage-approval stage, months earlier in the same purchase), so the figure is priced at this month, not last quarter.

5 · A range that means something

The range is measured, not assumed: we value thousands of homes that have already sold, using only what was known before each sale, and set the range so that about 8 in 10 of them sold inside it. Homes with their own recent sale and plenty of close neighbours get a tighter range; homes with thin local evidence get a wider one. If the range looks wide, that is the data being honest with you.

What we refuse to do

No asking-price averages. Many online estimates don't show their working. Ours lists every sale it used. We never average asking prices, because asking prices are hopes, not sales.
No invented figures. Where the data can’t support an estimate, we say so and show what public data does exist. A missing number is information too.
No hidden working. Every figure on a valuation page carries its sources, its sample size and its maths, on the page.

How accurate is it?

We test ourselves monthly: a sample of homes that just sold is valued using only the data available before each sale, then compared with what it actually fetched.

Median error

11.8%

Within 5%

21.5%

Within 10%

43.3%

Sample

600

Backtest month 2026-06, no-lookahead method (estimates use only pre-sale data). Homes were valued from their postcode and property type alone, as the free check does. 81.2% sold inside the range we would have shown.

Sources & attribution

Nationwide House Price Index, published by Nationwide Building Society.
Postcode geography via postcodes.io (Open Government / ONS sources).

Check My Postcode

Questions

Honest answers about the estimate

Is this a formal valuation?: No. It is an estimate computed from official public data. HM Land Registry sold prices, the UK House Price Index and the EPC register. A formal valuation is a RICS surveyor inspecting the actual property.
Why is your figure different from an estate agent’s?: An agent’s appraisal is a pitch to win your instruction, and it typically sits at or above the honest range. Our figure is built from what nearby homes actually sold for.
Why do you show a range instead of one number?: Because one number would overstate what the data can know. The range is set from our own track record: valuing homes that have already sold, using only what was known before each sale, about 8 in 10 sold inside the range we would have shown. Strong local evidence earns a tighter range; thin evidence a wider one.
What can’t your data see?: Condition, interiors, extensions that never triggered a certificate, and anything that has not sold or been certificated since records began. Interior condition alone can move a price by around 20%, which is one reason the range exists, and why you can tell us what you know.