House Price Index Explained

Whenever the news reports that house prices rose or fell by a certain percentage, the figure usually comes from the House Price Index. But what actually is it, and how much should you trust it?

The UK House Price Index (HPI) is an official monthly measure of how residential property prices are changing, produced by HM Land Registry using real completed sales. It tracks average prices and percentage changes at national, regional and local-authority level, and is one of the most authoritative free sources on the housing market.

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What the Index Measures

The HPI doesn't just average the sale prices in a given month. Doing that would be misleading, because the mix of homes sold changes constantly — a month with lots of flat sales would look cheaper than a month with lots of detached houses, even if nothing had actually changed.

Instead it uses a method that tracks the change in price for properties of similar type and characteristics over time. This "like-for-like" approach means the index reflects genuine price movement rather than shifts in what happened to sell.

How It's Calculated

The index draws on the full set of transactions registered with HM Land Registry, alongside data from the other UK land registries and valuation data. Because it covers actual completed purchases rather than asking prices or mortgage approvals, it captures what buyers really paid.

Key features to understand:

• It's a weighted measure, controlling for property type, so the mix of sales doesn't distort it.
• It's published for different geographies — UK-wide, nations, regions and individual local authorities.
• It reports both an average price and a percentage change (monthly and annual).

Why the Index Lags

The most important limitation is timing. A property sale takes weeks or months to complete, and only registers with the Land Registry after completion. As a result, the HPI you read today reflects deals agreed well before that.

This roughly two-month lag means the index is excellent for confirming trends but poor for spotting turning points in real time. If the market shifts suddenly, faster (but less complete) measures such as lender indices or asking-price surveys will move first. Our overview of signs the housing market will crash looks at the wider set of indicators worth watching.

How to Read It Sensibly

A few habits keep you from over-interpreting the numbers:

• Prefer annual change over monthly. Month-to-month figures are noisy and often revised.
• Zoom in geographically. The national headline can hide big regional differences; look at your own local authority.
• Expect revisions. Early estimates get updated as more sales register, so a figure can move after first publication.
• Remember it's an average. Your own home can outperform or lag the local index depending on its condition and improvements.

Using the Index for Your Own Home

The HPI is the engine behind a lot of useful personal calculations. You can apply your local percentage change to your purchase price to estimate how much your house has gone up in value, or to gauge your current loan-to-value before a remortgage.

Our house prices pages present this Land Registry data in a readable form, and the free house value calculator applies the index to your postcode automatically so you get a tailored estimate rather than a national average.

The Index and the Wider Economy

House prices don't move in isolation. Interest rates, wage growth and inflation all feed into demand and affordability, which in turn show up in the index months later. Reading the HPI alongside the Bank of England base rate gives a fuller picture than either on its own.

Is the House Price Index the same as Zoopla or Rightmove figures?

No. Portal figures are often based on asking prices or their own estimate models. The HPI uses completed, registered sales, which makes it more authoritative but slower.

Which House Price Index should I trust?

The official HM Land Registry UK HPI is the most comprehensive because it covers essentially all registered sales. Lender indices (such as those from major mortgage providers) are timelier but based only on their own approvals.

Why did the index get revised after I first read it?

Later sales for the same period continue to register, so early figures are provisional and firm up over the following months.

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Want to see what the index means for your property specifically? The free house value calculator applies your local House Price Index movement to your postcode for an instant, tailored estimate.