The Consumer Prices Index (CPI) rose by 3.4% on an annual basis in May – still significantly higher than the Bank of England’s 2% target.
Although this marked a slowdown compared to April’s reading of 3.5%, a data blunder from the Department for Transport meant the headline figure was overstated last month, and should have been 3.4%.
The Bank of England expects inflation to remain elevated over the coming months, peaking at 3.7% in September before falling back. Higher energy prices are largely responsible for the increase compared to last year, when inflation briefly returned to target.
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The underlying disinflationary process remains intact, according to the Monetary Policy Committee (MPC), however households will be following each report with trepidation, having been burned by the “transitory” narrative in the aftermath of the pandemic.
If you hadn’t heard of the Consumer Prices Index (CPI) before the cost-of-living crisis, you will almost certainly be familiar with the measure now thanks to its prominence in the news in recent years. But how does it differ from other measures calculated by the Office for National Statistics (ONS)?
We take a closer look at two key indices – the Consumer Prices Index and the Retail Prices Index (RPI). What does each measure tell you and which matters most for your finances? Plus, what is the Consumer Prices Index including owner occupiers’ housing costs (CPIH)?
What is CPI inflation?
CPI is the official measure of inflation. It tells you how much the cost of goods and services has increased over the past year based on a representative basket of household items. A new report is published each month. MoneyWeek’s calendar of CPI release dates tells you when you can expect the next figures.
CPI is recognised internationally as a statistic. This means the UK’s figures are closely comparable with those of other nations, even though its economy works in a different way.
To measure CPI each month, the ONS looks at around 180,000 prices across almost 750 typical goods and services to see how prices have changed. This shopping basket is reviewed each year to ensure the statistic keeps up with people's evolving spending habits.
The 2025 review reflected the latest trends in food, fashion and technology, with items such as pulled pork, men’s sliders and VR headsets joining the club. Old favourites like oven-ready gammon joints have been thrown out.
While this basket gives us an inflation figure, it is worth noting that inflation varies from household to household. For example, pensioners are likely to spend more on energy than young working professionals.
This means the recent increase in energy prices (1.2% at the start of January, followed by 6.4% at the start of April) is likely to hit pensioners’ budgets harder. The good news is that the Ofgem price cap will drop 7% from 1 July, however recent oil price spikes could mean higher bills this autumn.
You can see what your personal inflation rate is by using the inflation calculator from the ONS.
From state pension to benefits, how is CPI used?
As well as showing you how much your bills and purchases have gone up or down in price over the past year, CPI has a real-world impact on some day-to-day costs.
Each year, September's CPI report can play a key role in setting the state pension and other benefits like Universal Credit, public sector pensions and statutory sick pay.
Another thing to note with CPI is that the headline figure does not give you the full picture. Instead, it should be viewed as more of a broad sweep. The underlying data is often more insightful.
The Bank of England also looks at core inflation and services inflation when it decides how it will set interest rates. These two measures of inflation are running at 3.5% and 4.7% respectively.
Core inflation strips out categories that tend to see short, sharp fluctuations in prices, like food and energy.
Services inflation covers things like hotel stays, airfares, educational costs and more. Services make up around 80% of the UK economy, so this is an important measure of how embedded inflation is in the domestic economy.
What is RPI inflation?
RPI is another index used to measure changing prices. It came in at 4.3% in the latest report covering May 2025. RPI tends to track higher than CPI because it includes costs associated with home ownership.
Originally, RPI was the UK’s official inflation statistic. It was first implemented in 1956. “Until the introduction of the UK CPI […] in 1996, the RPI and its derivatives were the only measures of UK consumer price inflation available to users,” the ONS says.
Given its age, RPI can give us a sense of how prices have changed since the 1950s, but CPI replaced RPI as the UK’s official measure in 2003. The Bank of England’s 2% target relates to CPI.
Where RPI does still have relevance is when it comes to setting cost increases for some bills and services. For example, it is used by the government to set annual rail ticket price increases. It is also used to set levies like road tax.
Here are some of the other things RPI sets or influences:
- Tobacco duty
- Air passenger duty
- Alcohol duty
- Final salary pension payments
- Interest on student loans
- Income from index-linked annuities
What is CPIH inflation?
CPIH is another measure calculated by the ONS. It stands for the Consumer Prices Index including owner occupiers’ housing costs. It came in at 4% in May.
CPIH is similar to CPI, but includes the costs of owning, maintaining and living in a home. This means it also shares characteristics with RPI.
CPIH is the ONS's best measure of UK inflation given it captures more of the economy than the other two measures. However, given the UK housing system is different to that of any other nation, it is not internationally comparable.
What does high inflation mean?
High inflation means costs are rising at a rapid rate. Unless your money keeps up (for example, in an inflation-busting savings account or through wage increases) the value of your cash will erode over time.
Imagine your savings are earning a low rate like 2% interest and inflation is 3.4%. That means your savings are being eroded at a rate of 1.4% in real terms. Similarly, if you get a 5% pay rise and inflation is around 3.4%, your real wage increase is more like 1.6%.
Most western economists agree that having a manageable rate of inflation is not a bad thing. The problem in recent years has been price increases getting out of control.
The Bank of England has a remit to keep inflation at 2% – a level it believes allows for a good level of spending that will boost economic growth. The reason is that, if prices are going up in the near future, you might as well complete a purchase today.
Putting some money into a diversified portfolio of investments (such as a global stock market tracker) can be a good long-term strategy for trying to beat inflation. Investments typically beat cash over the long run, but a minimum horizon of five years is generally recommended.
We take a closer look in our guide on saving versus investing.
What is the impact of low inflation?
Low inflation means prices are rising at a slow rate. Meanwhile, deflation means prices are falling. If sustained for a long period, low inflation and deflation can indicate a weaker economy, with deflation likely to be particularly bad for GDP growth.
If inflation comes in below the Bank of England’s 2% target, most economists believe spending will generally decrease. With wages likely to outpace the rate of price rises, consumers are more likely to be incentivised to hold onto their disposable income, which means less money will move around the economy and the government's tax revenues will fall.
In a deflationary scenario, these effects are likely to be turbo-charged. After all, why spend your money now if what you are buying could be cheaper next week? Deflation is different from disinflation, which is when prices are still rising but at a slower rate than they once were.
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