The consumer price index or consumer price index[1]​ (commonly called by its acronym CPI) is an economic index in which the prices of a certain set of goods and services are valued (known as "family basket" or "basic food basket) determining, on the basis of the continuous family budget survey (also called "household expenditure survey"), that a number of consumers acquire on a regular basis, and the variation with regarding the price of each one, compared to a previous sample. It measures changes in the price level of a basket of consumer goods and services purchased by households.

This is a percentage that can be positive (indicating an increase in prices) or negative (reflecting a fall in prices).

It is an indicator widely used by governments to measure inflation.

It is assumed that every CPI should be:.

The objective is to measure the evolution of the prices of goods and services representative of the consumption expenditures of households in a region. The uses that are usually given are:

Generally we see that the loans requested in various financial institutions are reflected in UF or UTM, since the CPI will also readjust to such indicators, so the effect of inflation on said debts will be more easily reflected.

The main criticisms that are usually mentioned regarding the CPI (and any price index) are generally the following:

These are the most common. However, they are not applicable to the CPIs of all countries. Each country publishes a methodology on the occasion of the CPI base change detailing how they resolve these and other problems. Most countries follow international recommendations, among which those in the International Labor Organization manual stand out.