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House value calculator by postcode: how it works and how far to trust it

How a house value calculator by postcode works: Land Registry sales, the UK House Price Index, what the data cannot see and how to judge the result you get.

5 min read
Last reviewed 20 October 2026
By Your Property Check team

Part 1 of 8

What happens when you type in a postcode

Every postcode calculator follows the same basic steps. Seeing them makes it easier to judge any result, ours or anyone else's.

Find sales nearby. It looks up homes that have sold in your postcode and the streets around it.
Keep like with like. It should compare the same type of home: a detached house with detached houses, a flat with flats.
Move old prices to today. A sale from a few years ago is out of date, so the price is adjusted by how the market has moved since.
Combine and show a result. The sales are weighed, with closer and more recent ones counting for more, and shown as a figure or a range.

Some calculators then add things the sales data cannot know, such as the floor area from an energy certificate. A good one tells you when it has done so.

Part 2 of 8

Where the data comes from

Sale prices. HM Land Registry's Price Paid Data covers residential property sales in England and Wales that were sold for value and lodged for registration. It is released under the Open Government Licence, which allows commercial and non-commercial reuse. That is why many sites can show the same sold prices.

The index. The UK House Price Index is published monthly by HM Land Registry, with the Office for National Statistics calculating it from sales records. It shows how prices have moved by area and property type, with history going back to 1995 for England and Wales.

Part 3 of 8

An illustration of moving an old price forward

The numbers below are made up to show the idea. They are not a real home or a real area.

Step	Illustration
A similar home sold when the local index stood at	100
The index for the same area and type now stands at	108
The old sale price is moved up by	8%

If that sale were the only evidence, today's equivalent price would be 8% above the old one. Real calculators combine many sales rather than relying on one, and use the index for the right area and property type.

Part 4 of 8

Why the postcode is only the starting point

A postcode usually covers a small cluster of homes, but those homes can differ a lot. Some may be flats, some terraces, some larger detached houses. A calculator that averages them all gives you a number that fits nobody. That is why the type of home matters more than the postcode alone.

When few similar homes have sold in your postcode, a good calculator widens the search in steps: your street, nearby postcodes, then the wider district. It should also count the nearest and most recent sales most heavily, and show a wider range when the evidence is thin.

Part 5 of 8

What the data cannot see

This is the part most calculators bury. The sold price records tell you what a home sold for. They tell you nothing about the home.

Not in the data	Why it matters
Condition and decoration	Two identical houses can sell at very different prices
Extensions, loft or garage conversions	Often not recorded against a sale
Garden, parking, noise, view	Differ house to house, even in one street
Leasehold terms	Lease length, ground rent and service charge change a flat's appeal
Sales that are not recorded	HM Land Registry's guidance lists exclusions such as gifts, right-to-buy discount sales and transfers on divorce
The most recent sales	Registration typically lags a sale by 2 weeks to 2 months, so the latest two months are incomplete
Scotland and Northern Ireland sales	The Price Paid Data covers England and Wales only

The index has a limit too. Its own page warns that local authorities with few sales can show volatile monthly movements, so longer-term trends are safer than a single month.

Part 6 of 8

So how accurate is it?

Be wary of any calculator that gives one precise figure and no range. A single number claims more than the data can know.

What you can fairly expect is this: the result is more reliable when many similar homes have sold nearby recently, and less reliable when your home is unusual, the area has few sales, or the property has been changed since it last sold. A postcode with only a handful of sales in recent years gives a weak result whoever builds the calculator.

We publish our own method on how we value, including what the estimate cannot see, so you can check it rather than take our word for it.

Part 7 of 8

What our calculator does

Our free house value check works like this, in plain terms:

It starts with recent sales of the same type of home, nearest first: your postcode, then your street, then neighbouring postcodes, then the wider district.
It moves each sale to today using the official index for that property type.
It uses your home's own previous sale if there is one, and the floor area from an energy certificate if one is on record.
It shows a range, not a single figure.

It is an estimate, not a formal valuation. It cannot inspect your home. A surveyor gives a formal valuation. The step-by-step way to get a fuller picture is in our guide on how to find out how much your house is worth.

Part 8 of 8

Five questions to ask of any calculator

Does it show a range or only one figure?
Does it say which sales it used, and how recent they are?
Does it compare the same property type?
Does it say what it cannot see?
Does it ask for your email before showing a result? Think about why.

This page is general information, not valuation advice.

Questions, answered

Frequently asked questions

How does a house value calculator by postcode work?

It finds recent sale prices of similar homes near your postcode in HM Land Registry data, moves each price on using a house price index, then combines them into an estimate. It cannot see your home, so it works best as a range and a starting point.

How accurate is a house price by postcode?

It depends on how many similar homes sold nearby recently, and how typical your home is. It cannot see condition, extensions or fittings. Treat it as an estimate range, and check it against local agents and sold prices on your own street.

Where does a UK house value calculator get its data?

Mostly from HM Land Registry Price Paid Data, which covers residential sales in England and Wales and is released under the Open Government Licence, plus the UK House Price Index to update old prices. Some also use energy certificate data for floor area.

Why is the result different from an estate agent's figure?

A calculator uses past sales and cannot see the property. An agent can visit and see condition, but is also hoping to win your instruction. Ask the agent which sales they used and compare with the calculator's range.

Does the calculator include Scotland?

The HM Land Registry Price Paid Data covers England and Wales only. Scotland and Northern Ireland have separate registers, so a calculator built on that data cannot value homes there in the same way.

Where this comes from

Sources

Last reviewed 20 October 2026 by the Your Property Check team. This page is general information, not legal, tax or financial advice. For your own situation, speak to a conveyancing solicitor or another qualified professional.