The Consumer Price Index (CPI) is a statistical estimate of the prices of goods and services purchased by households for consumption. It is calculated from a weighted basket of consumer goods and services, with the weights reflecting patterns of household spending.

Changes in the CPI are commonly used to track inflation over time. Prices are collected periodically from retail and service establishments, and the contents and weights of the basket may be updated to reflect changes in consumer spending. Statistical agencies may also adjust for differences in product quality so that the index is intended to capture price changes rather than changes in the characteristics of goods and services.

In the United States, consumer price indices are published monthly by the Bureau of Labor Statistics. The CPI-U is the most widely cited measure of consumer inflation, while other versions are used for different purposes. The CPI is one of several measures of price changes and is not a perfect measure of the cost of living.

In the news context, the U.S. Consumer Price Index was reported as 3.7 per cent higher in September than a year earlier, with fuel and clothing prices among the main contributors to the increase.