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. Our range is the real spread of the comparable evidence — a street where everything sells for similar money gets a tight range; a mixed street gets a wide 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.

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 · Size — local £/m² × this home’s own floor area

Size is the biggest driver a blind average can’t see: one street can honestly span £380,000 to £617,000 simply because its houses range from 88m² to 150m². Where the property and enough neighbours have a measured floor area on the EPC register, we price by the going rate per square metre — the same normalisation professional tools are built on.

2 · This home’s own sale, carried forward two ways

A previous sale of the same home is the strongest single fact there is. We carry it forward on the official UK House Price Index for its own property type and area — and separately by its standing: if it sold 10% above its street’s typical value then, it’s likely about 10% above it now. Two independent routes; when they agree, that agreement is the confidence signal. If the Land Registry record is missing your sale (its record has real gaps), you can tell us what you paid — always labelled as your figure, never dressed up as a registry fact.

3 · Weighted comparable sales

Every nearby sale is uplifted to today by the official index for its own property type, then weighted by how comparable it truly is: the house next door on the same postcode counts around six times as much as an anonymous sale a mile away, a flat is never evidence for a house, and outliers are trimmed. The comparables — and the weight each one carried — are shown, not hidden.

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 the actual spread of the evidence, capped between 5% and 15% — not a fixed percentage stuck on every property. A consistent street earns a tight range; a varied one earns a wide one. If the range looks wide, that is the data being honest with you.

What we refuse to do

No asking-price averages. Some free “instant valuations” are the average of a few nearby asking prices with ±10% bolted on. Asking prices are hopes, not sales — averaging them produces a bigger, more flattering, less accurate number. We never use them.
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 measure it rather than claim it. Each month we value a sample of homes that have just sold — using only the data available before each sale — and compare our estimate with the achieved price. The first published results will appear here once our first full monthly backtest completes. Until then we make no accuracy claim at all — which is more than most valuation tools can say.

Sources & attribution

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

See it work on your 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. Our range is the real spread of the comparable evidence — a street where everything sells for similar money gets a tight range; a mixed street gets a wide 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.