CPI — the index
A unitless number anchored so that 1982–1984 average prices equal 100. It answers "how expensive is the basket compared with the reference period?" A level on its own tells you nothing about whether prices are rising quickly.
CPI vs inflation
They are related but not the same. CPI is a level — currently 336.9 for Sep '26. Inflation is how fast that level is changing — +4.00% over the past twelve months. One number describes prices; the other describes their movement.
Inflation — the rate
A percentage change in that index over a stated window: twelve months, one month, or an annualized three- or six-month pace. It answers "how fast are prices rising right now?" and it is the number policy and pay decisions react to.
Inflation measures compared, Sep '26
live feed · measures without a configured source are omitted
| Measure | Published by | 12-month rate | Month over month |
|---|---|---|---|
| BLS CPI-U | U.S. Bureau of Labor Statistics | +4.00% | +0.59% |
| Core CPI (ex food & energy) | U.S. Bureau of Labor Statistics | +2.82% | +0.37% |
| BLS CPI-W | U.S. Bureau of Labor Statistics | +4.21% | +0.66% |
| Chained C-CPI-U | U.S. Bureau of Labor Statistics | +3.85% | +0.55% |
Questions people ask
Is CPI the same as inflation?
No. CPI is an index level that measures the cost of a basket of goods and services. Inflation is the rate at which that index changes, usually quoted over twelve months. CPI is the thermometer; inflation is the temperature change.
Which inflation rate does the news quote?
Almost always the year-over-year change in the headline CPI-U, not seasonally adjusted. When a report says inflation came in at a given percent, that is the twelve-month change in the CPI-U index.
Why does the Federal Reserve target PCE instead of CPI?
PCE from the Bureau of Economic Analysis covers a broader definition of consumption and updates its weights more frequently, which the Fed considers a better read on the underlying trend. Its 2 percent target refers to core PCE, not CPI.
Which measure should I use in a contract or a raise discussion?
Most escalation clauses reference CPI-U or CPI-W for a stated area and period. CPI-W drives Social Security cost-of-living adjustments. Whatever you choose, name the exact series and reference month in writing.