Core inflation is a measure of price change that leaves food and energy out of the calculation. Economists and other data users examine it because those prices can move sharply from month to month, potentially obscuring broader patterns. But “core” does not mean more real, or more relevant to every household. The full index includes the purchases consumers make, including groceries and gasoline. Each measure offers a different view: one tracks the whole basket, while the other helps show whether price increases are spreading beyond volatile categories.
A filter for a particular question
The Consumer Price Index measures average changes over time in prices paid by consumers for a representative basket of goods and services. The Bureau of Labor Statistics publishes an all-items measure and an index for all items less food and energy. The second is commonly called core inflation. It removes those categories from the calculation; it does not assert that they are unimportant or that prices in the remaining basket are stable. Bureau of Labor Statistics
Food and energy are excluded because their prices can be relatively volatile. A jump in gasoline can make the monthly all-items number rise even if many other prices are changing more gradually. Looking at the measure without food and energy can help analysts focus on that broader pattern. It is a lens for examining price movement, not a replacement for the full index or a forecast of what will happen next. Bureau of Labor Statistics
What September’s split shows
September 2026 provides a clear example. The seasonally adjusted all-items CPI rose 0.6 percent from August, while the index excluding food and energy rose 0.3 percent. Gasoline prices rose 9.1 percent that month and accounted for more than half of the monthly all-items increase. The food index was unchanged. These figures show how a large move in one excluded category can pull the headline measure above core in a given month. Bureau of Labor Statistics
The comparison does not mean every household’s costs rose by either 0.6 or 0.3 percent. The CPI represents an average basket, and an individual’s spending pattern may differ. Someone who drives frequently may feel a gasoline jump more directly; a household with little fuel use may be less exposed. Nor does one month establish a lasting trend. September’s 12-month all-items increase was 3.7 percent, compared with 2.6 percent for all items less food and energy. The time period matters as much as the measure. Bureau of Labor Statistics Bureau of Labor Statistics
The grocery-and-gas distinction
Imagine a month in which gasoline rises sharply while grocery prices are flat. The full CPI records both facts: the fuel increase and the lack of change in food. Core CPI leaves both food and energy out, so it can show whether prices such as rent, medical care, clothing, or recreation are still increasing. A reader asking, “What happened to the broad basket people buy?” needs the all-items measure. A reader asking, “Are price increases visible outside food and energy?” may find core more useful.
This distinction also explains why core can diverge from the experience at the pump or checkout. In September, food at home fell 0.1 percent and food away from home rose 0.2 percent; together the food index was unchanged. Meanwhile, the gasoline index rose sharply. The average index is not a receipt for a particular family, and the core measure deliberately excludes the categories that may loom largest in a particular budget. Bureau of Labor Statistics Bureau of Labor Statistics
CPI core and PCE core are separate measures
There is also more than one core inflation measure. The Federal Reserve’s preferred inflation gauge is often discussed using the Personal Consumption Expenditures price index, which BEA publishes separately from the CPI. In September, the PCE price index rose 3.6 percent over the year; excluding food and energy, it rose 3.1 percent. These are not CPI figures. The CPI’s corresponding annual changes were 3.7 percent overall and 2.6 percent excluding food and energy. Different indexes can produce different readings because they are distinct measures. Bureau of Economic Analysis Bureau of Labor Statistics
The practical answer is to match the statistic to the question. Headline CPI helps describe price changes across the consumer basket, including necessities that a core calculation omits. Core CPI helps isolate movement outside food and energy, where a volatile month might otherwise dominate the signal. Neither one measures an individual household’s exact inflation rate, and neither alone explains why a price changed. Reading both, with the period and index clearly identified, gives a fuller account of what is rising and what is being left out.
Sources & further reading
- Consumer Price Index questions and answers ↗Bureau of Labor Statistics
- September 2026 Consumer Price Index ↗Bureau of Labor Statistics
- September 2026 personal income and outlays ↗Bureau of Economic Analysis
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