How do I calculate the percentage change in prices between two periods in time?
Data from table 3.1 of ‘Focus on Consumer Price Indices’ should be used with this formula: [(Later date CPI – Earlier date CPI)/ Earlier date CPI]x100 Users should be aware that the CPI uses unrounded indices to calculate percentage changes. Therefore, if the published rounded figures in table 3.1 are used in the calculation of rates, the result will not always give the correct value when rounded to one decimal place. If you require unrounded values, please contact the CPI team directly on cpi@ons.gov.uk.
