To read a consumer price index (CPI) table, it is important to know that most CPI tables use a base reference, which is the time period between 1982 and 1984 and changes in indexes for other time periods are in relation to this reference base, as noted by the United States Department of Labor's Bureau of Labor Statistics (BLS). The CPI, which is calculated each month, shows the average change of prices of the goods and services bought for consumption. The CPI also can be an economic indicator of inflation.
The BLS can use different types of CPI statistics, such as the CPI-W or CPI-U. However, a comprehensive CPI that is often used is the CPI-U, or the all-item CPI for all urban consumers, where the reference base is 1982-1984 = 100. To use this type of CPI chart or table, consumers need to look up the CPI for a particular month of a year and subtract 100 from the given CPI value to find the rate of increase or decrease in prices for that time period, as noted by the BLS.
The U.S. Inflation Calculator website provides a table for CPI data from 1913 to 2015. To use this table to find, for example, the price increase for the month of June 2015, consumers just need to look up the CPI for this month, which is given as 238.638. Subtracting 100 from this value gives a price increase of 138.64 percent. This means an inflation rate of 138.64 percent since 1982.