Inflation Calculator UK

What inflation actually measures

Inflation is the rate at which prices rise, and the UK’s main measure is the Consumer Prices Index (CPI), published every month by the Office for National Statistics (ONS). The ONS tracks the prices of hundreds of goods and services — food, housing, transport, clothing, recreation — in a “basket” that is meant to represent what a typical household buys, and turns it into an index. The index is set so that 2015 equals 100. When the index is 144.1, as it was in September 2026, prices are on average 44.1% higher than they were in 2015. The annual inflation rate — 3.5% in the year to September 2026 — is the percentage rise in the index over the previous twelve months.

To work out what old money is worth today, you divide the index today by the index in the old year and multiply by the amount. £100 in 2000, when the index was 72.7, becomes £100 × 144.1 ÷ 72.7 = £198.21. That does not mean a specific thing that cost £100 in 2000 costs £198.21 now — some things have risen faster than the average and some slower. It means the general level of prices has roughly doubled, so £100 of 2000 spending power needs £198.21 today.

CPI index values used (ONS, 2015 = 100)

The table tells the story of the last few years plainly. Prices rose 9.1% in 2022 alone — the index jumped from 111.6 to 121.7 — the fastest rise in decades, driven by energy and food prices. They rose another 7.3% in 2023, then slowed: 2.6% in 2024 and 3.4% in 2025. But slowing inflation does not mean prices fall. It means they rise more slowly. The £100 of 2021 spending power that needed £118.41 by 2022 still needs £129.12 today. Once prices rise, they stay up unless there is deflation, which the UK has not seen in this series.

Why your own inflation is different from CPI

CPI is an average, and nobody is average. If you rent, your housing costs may have risen faster than the index. If you drive a lot, fuel matters more to you than to a household that does not. If you spend most of your money on food, the food index matters more than the overall one. The ONS basket is updated every year to reflect what people actually buy — streaming services in, DVD players out — but it can never match one household exactly. So treat the calculator’s answer as the general change in the price level, not as a precise measure of your own cost of living. If your pay has risen by less than cumulative inflation since a given year, your real pay — what it actually buys — has fallen, even though the number on the payslip went up.

What inflation means for savers

Inflation is the reason a savings account paying 4% is not really paying 4%. If inflation is 3.5%, the real return — the increase in buying power — is only about 0.5%. And if inflation is higher than your interest rate, your money is losing buying power even while the balance grows. That is why the Bank of England’s target is 2% a year: at 2%, prices double roughly every 35 years, which is slow enough to plan around. At 9%, as in 2022, prices double in about eight years. The calculator shows the same idea in reverse: money left in a drawer since 2000 has lost half its buying power. Cash is safe from market falls, but it is not safe from inflation — which is why long-term savings usually need a return above inflation, whether from an ISA, a pension, or investments, to hold their value.

Using this for pay rises, pensions and house prices

The calculator’s most useful job is not nostalgia — it is checking whether a number has really gone up. Take pay: a £30,000 salary in 2020 needs to be £39,770 in September 2026 just to buy the same things, because prices rose 32.57% in between. If the pay is now £36,000, it looks like a £6,000 rise, but in real terms it is a pay cut of about £3,770. That is the calculation to do before accepting a pay offer, and it is the same maths for a pension: a pension that pays £10,000 a year and never rises will buy what £7,441 buys today after ten years at 3% inflation, and what £5,537 buys after twenty years. A pension that rises with inflation holds its value; one that does not, quietly shrinks.

The same idea applies to savings targets. If you want £50,000 in today’s money in ten years’ time, and inflation averages 3% a year, you will need about £67,200 in ten years’ money to buy the same things. That is why long-term plans should be set in today’s money and then adjusted for inflation, rather than set as a fixed future number that inflation will eat. House prices are the most common place people forget this: a house that “doubled” from £100,000 in 2000 to £200,000 today has barely kept pace with general prices, which rose 98% over the same period. It doubled in pounds, but it did not double in buying power.

CPI, CPIH and RPI: which measure is this?

This calculator uses CPI, the ONS’s headline measure and the one the Bank of England targets at 2% a year. There are two others you may meet. CPIH is CPI plus the cost of owning and living in your own home, and it usually runs a little above or below CPI by a few tenths of a percent. RPI is an older measure that almost always runs higher than CPI, and it is still used for some things, such as student loan interest and some rail fares. The differences matter if you are comparing two figures that use different measures, but for working out what old money is worth today, CPI is the standard choice, and it is the one this page uses throughout.

Related: ISA Savings Calculator · Compound Interest Calculator · Take Home Pay Calculator

Sources: Office for National Statistics, Consumer price inflation, UK: September 2026 (CPI 12-month rate 3.5%; CPI index series D7BT, 2015 = 100); ONS CPI time series annual averages 2000–2025. “Today” is September 2026 (index 144.1); October 2026 CPI was due 18 November 2026. Checked 13 November 2026.