The British pound experienced an average inflation rate of 2.75% per year between 2000 and 2017. £100 in the year 2000 is worth £158.58 in 2017.
The current inflation rate in 2017 is 2.70%1.
How to calculate inflation since 2000
Start with the CPI inflation formula:
CPI in 2017 / CPI in 2000 * 2000 GBP value = 2017 GBP value
Then plug in historical CPI values. The UK CPI was 671.8 in the year 2000 and 1065.34818 in 2017:
1065.34818 / 671.8 * £100 = £158.58
The "purchasing power" of £100 from 2000 is £158.58 in 2017.
Source: This calculator uses the composite price index published by the UK Office for National Statistics (ONS). A composite index is created by combining price data from several different published sources, both official and unofficial. The Consumer Price Index, normally used to compute inflation, has only been tracked since 1988. All inflation calculations after 1988 use the Office for National Statistics' Consumer Price Index, except for 2017, which is based on The Bank of England's forecast.