There is a formula with which be able to obtain the inflation rate, taking as reference a period specific of time and the CPI of the same one. The formula is:
[ (final CPI - CPI initial) / CPI inicial] x 100
This CPI, acrónimo of Consumer price Index, represents the evolution of the price of the goods and services of a country over a year. For example, if a bottle of water voucher an euro to beginning of 2019 and 1.5 euros to end of 2019, this index us shows the percentage of growth of the cost of the above-mentioned product. Your calculation it carries out in National Statistics Institute (INE) on the basis of a shopping basket standard compound, to this day, for 479 items (and 220,000 realized prices of 22,000 accommodated shops in 177 municipalities different).