Use this calculator to find the equivalent buying power over time for an amount in US dollars.
Consumer Price Index (CPI) Inflation Calculations
Converting buying power from one year to another is done by a ratio calculation using the starting value and the CPI's for the years being compared. Converting from Year 1 to Year 2 we state: Dollars in Year 1 is to Dollars in Year 2 as CPI in Year 1 is to CPI in Year 2.
DollarsYear1 / DollarsYear2 = CPIYear1 / CPIYear2, solving for DollarsYear2
DollarsYear2 = DollarsYear1 * CPIYear2 / CPIYear1
Example: $10.00 in 1980 has what buying power in 2010? From the table, CPI 2008 = 82.4 and CPI 2010 = 218.056. Converting we use:
DollarsYear2 = DollarsYear1 * CPIYear2 / CPIYear1 = $10.00 * 218.056 / 82.4 = $26.46. What cost $10.00 in 1980 would cost $26.46 in 2010.
Total inflation from Year 1 to Year 2 is a percentage change, positive or negative, and is a percentage change calculation.
Percentage change = ( ΔV / |V1| ) * 100 = ((V2 - V1) / |V1|) * 100
Calculating change from 1980 to 2010 using CPI:
Inflation = ( ΔV / |V1| ) * 100 = ((V2 - V1) / |V1|) * 100 = ((218.056 - 82.4) / |82.4|) * 100 = 164.63%.
Calculating change from 1980 to 2010 using known "buying power:"
Inflation = ( ΔV / |V1| ) * 100 = ((V2 - V1) / |V1|) * 100 = (($26.46 - $10.00) / |$10.00|) * 100 = 164.6%.
Inflation Index : CPI Table
The US government has been calculating the CPI since 1913. This calculator uses the yearly averages from the U.S. Bureau of Labor Statistics and when a full year of data is not available we use the latest month available in that year. You can find the most recently updated tables here and other consumer price index information and facts at the U.S. Bureau of Labor Statistics website along with their CPI Inflation Calculator.
Keep in mind that this is a cumulative total for urban areas and the government applies much more detail to the analysis of different aspects and sectors that affect the CPI.
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