Purchasing power over time
Inflation at a glance
| Year | CPI Index | £100 in 2000 is worth |
|---|
How UK inflation is calculated
Inflation measures how much prices have risen over time. The UK uses the Consumer Prices Index (CPI), maintained by the Office for National Statistics, as its primary inflation measure. CPI tracks the cost of a basket of around 730 goods and services that represent typical household spending.
Comparing prices between years
To find what an amount from one year would be worth in another year, multiply by the ratio of the two CPI values. For example, to find what £100 in 2000 is worth today (September 2026): £100 x (144.1 / 72.7) = £198.21. £100 in 2010 is worth £100 x (144.1 / 89.4) = £161.19.
Calculating the total inflation rate
This gives you the total percentage change in prices between the two years. Between 2000 and September 2026, total inflation was approximately 98.2%.
Annualised inflation rate
The annualised rate tells you the average yearly inflation over the period. This is useful for comparing inflation across periods of different lengths. Between 2000 and September 2026, the annualised rate was approximately 2.6% per year.
CPI base year
The CPI index uses 2015 as its base year (2015 = 100). All other years are expressed relative to this baseline. A CPI of 144.1 in September 2026 means prices are 44.1% higher than the 2015 average.
Where the figures come from
Every figure in this calculator is the ONS CPI index, series ID D7BT (CPI INDEX 00: ALL ITEMS, 2015=100, dataset MM23). Years 1988 to 2025 use the ONS annual average. 2026 uses the latest published month, September 2026 (144.1, released 21 October 2026), because a full-year 2026 average does not exist yet. Figures fetched from the ONS D7BT series page on 30 October 2026. The next ONS release is due on 18 November 2026.
Worked examples
Each example below was run through the calculator above with the inputs shown. Past years use the ONS annual average CPI; 2026 uses the September 2026 index, the latest published.
Has a £30,000 salary from 2020 kept up?
Enter £30,000, from 2020, to 2026. To buy the same in September 2026 you would need £39,770.01, because prices rose 32.57% over the period. If the same job now pays less than that, its pay has fallen in real terms, even if the number on the payslip went up. The calculator compares prices only; it does not know what happened to tax or National Insurance on that salary.
£1,000 from 1990 at September 2026 prices
From 1990 to 2026 the answer is £2,577.82, total inflation of 157.78%. Prices have more than doubled, so a sum saved in 1990 and never invested would buy well under half what it did then.
The 2021 to 2023 price surge
£100 in 2021 had the buying power of £116.94 in 2023: prices rose 16.94% in two years, an annualised 8.14%. The ONS annual CPI rate was 9.1% for 2022 and 7.3% for 2023, against 2.6% in 2021 (ONS CPI annual rate, series D7G7, checked 30 October 2026).
Rules that change the answer
CPI, CPIH or RPI
This calculator uses CPI, the measure the Bank of England is set to keep at 2% (Bank of England: inflation, checked 30 October 2026). The ONS also publishes CPIH, which adds owner occupiers' housing costs, and the older RPI. In the 12 months to September 2026, CPIH rose 3.6% and CPI 3.5%. The ONS says RPI does not meet the standard for accredited official statistics but still publishes it because many contracts use it (ONS consumer price inflation, September 2026, checked 30 October 2026). If your contract, rent review or pension is linked to RPI, use the RPI series instead, because the two give different answers.
Annual averages against a single month
A year's figure here is the average of its twelve monthly indexes, so "2020" means prices across 2020, not on 1 January. The latest year is a single month. When the end year is 2026, the annualised rate measures the time from the middle of the start year to mid-September 2026, so 2000 to 2026 counts as about 26.2 years, not 26.
How far back it goes
The ONS CPI index series D7BT starts in 1988, so the calculator does too. The next CPI release is due on 18 November 2026, after which the latest month will move on.
Common mistakes
Reading a falling inflation rate as falling prices. When the rate drops from 9.1% to 7.3%, prices are still rising, just more slowly. Prices only fall when the rate is below zero.
Applying this year's rate to a whole period. 3.5% is the change over the last 12 months only. For a longer stretch, compare the two index values as this calculator does.
Treating a personal cost as the average. CPI tracks a basket of household spending. Your own costs, such as rent, energy or childcare, can rise faster or slower than the average.
How this calculator works: it multiplies your amount by the ratio of the two CPI index values, and reports the total change and the compound yearly rate between them. Index values come from ONS series D7BT, last fetched on 30 October 2026. For background on inflation measures, see our UK inflation guide; every source is listed on our methodology page.