How to work out how much house prices have changed
A common question is how much prices in a postcode have gone up since a particular year, such as 2020. The sum itself is simple. The harder part is making sure the two figures you compare are describing the same kind of homes.
This guide shows the calculation with an example, explains the two main ways of measuring change, and covers the things that most often make a result look bigger or smaller than it really is.
The basic calculation
Take the typical sold price for the later period, subtract the typical sold price for the earlier period, divide the result by the earlier price and multiply by 100. That gives the percentage change.
As an example with round illustrative numbers: if the median sold price in a postcode district was £250,000 in 2020 and £300,000 in 2025, the change is £50,000. Divide £50,000 by £250,000 and you get 0.2, which is a rise of 20%.
Always divide by the earlier figure, not the later one. Dividing £50,000 by £300,000 gives about 17%, which understates the rise. If prices fell, the same method gives a negative percentage.
To compare periods of different lengths, you can also work out a yearly average. A 20% rise over five years is not 4% a year compounded, because each year builds on the last. The compound rate in the example is a little under 4% a year.
Median prices or repeat sales
There are two broad ways to measure change. The first compares a typical price, usually the median, for all sales in each period. This is what most local price figures do, including the figures on House Price Monitor. It is easy to follow but is affected by which homes happened to sell in each period.
The second looks at repeat sales: the same property sold twice, with the change in its own price measured between the two sales. Because the home is the same, the mix problem largely goes away. The drawback is that only homes that sold twice count, and any work done to the property in between, such as an extension, shows up as price growth.
If you know a particular home sold in an earlier year, you can do a repeat sales check yourself. Find both sales, then apply the same percentage calculation. Our guide on how to find what a house sold for explains where to look.
For why the median is used rather than the average, see average vs median house price.
Checklist
- Use the same measure, ideally the median, for both periods
- Divide the change by the earlier price
- Compare whole years rather than single months
- Check how many sales sit behind each figure
- Compare one property type at a time where you can
- Separate new build sales if a development completed
- Avoid the last two months, which are still filling in
- Check the result against the UK House Price Index for the local authority
Small samples swing more
The fewer sales behind a figure, the more one or two unusual sales can move it. A postcode district with several hundred sales a year gives a steady median. A single street with four sales in a year does not.
As an example, if a street had three sales in 2020 and three in 2025, the change between those two medians says more about which three homes sold than about the market. A large detached house selling in one year and two small flats in the other can produce a big jump or fall with no real change in values.
It helps to compare whole years rather than single months, and to use the wider area when a street or small postcode has few sales. Where the number of sales is low, treat the percentage as a rough guide only.
The mix of property types
Price change is most reliable when you compare like with like. If more flats sold in one year and more houses in the other, the median will move even if no individual home changed in value.
HM Land Registry records each sale as detached, semi-detached, terraced, flat or maisonette, or other. Where you can, work out the change for one property type at a time. A change for terraced houses only, for example, is easier to trust than a change for all sales together.
New build homes are worth watching too. A large new development completing in one year can lift the median for that year, because new homes often sell at a premium. The Price Paid Data marks each sale as new build or established, so you can separate them.
Tenure matters in the same way. Leasehold flats and freehold houses behave differently, and a shift between them changes the median.
Allow for the newest months
Sales take two to eight weeks to be registered after completion, so the most recent month always has fewer sales than it will have later. If your later period includes the last month or two, the figure may move once more sales come in.
Using full calendar years, or a period that ended a few months ago, avoids this. See why sold prices take months to appear for more on the lag.
The UK House Price Index as a benchmark
The UK House Price Index is the official measure of house price change. It is produced by HM Land Registry and the Office for National Statistics, with the other UK land registries, and published every month.
It is mix adjusted. Instead of comparing raw medians, it uses details such as property type, size and location to adjust for the kind of homes that sold, so a shift towards bigger or smaller homes does not distort the figure. Recent months are revised for up to a year as more sales are registered.
The index is published for the UK, countries, regions and local authorities, not for postcode districts or streets. That makes it a useful check on a local figure. If your postcode shows a 30% rise and the local authority shows 15% over the same period, look at sample size and property mix before concluding that your area did much better.
Prices for your postcode
Postcode and street pages on House Price Monitor are free to read and show the median sold price from HM Land Registry data. You can find yours on the postcodes page.
The full monthly report for a postcode district lists every sale and is £4.99 a month, with the first report free on sign-up. These are completed sales, not valuations or forecasts.
Other guides
Why sold prices take months to appear
Comparing house prices between streets and postcodes
What the Land Registry price data includes
How to find what a house sold for