Choose a price index, such as the Consumer Price Index (CPI)
Get the index value for the earlier period
Get the index value for the later period
Subtract the earlier index value from the later index value
Divide the result by the earlier index value
Multiply by 100
Use the formula: Inflation rate = [(Later CPI – Earlier CPI) / Earlier CPI] × 100
If using prices instead of an index, use: Inflation rate = [(New price – Old price) / Old price] × 100
Express the result as a percentage