One rate, eight groups
The consumer price index is built from eight major groups: housing, transportation, food and beverages, medical care, education and communication, recreation, other goods and services, and apparel. Each carries a weight, its share of the national basket, and the headline rate is the weighted average of their price changes.
In December 2025 the weights were housing 44.5%, transportation 16.3% and food and beverages 14.5% — three-quarters of the basket between them. Medical care was 8.4%, education and communication 5.8%, recreation 5.1%, other goods and services 2.9% and apparel 2.4%.
What moved in the year to August 2026
Prices rose 3.4% over the year. Underneath, the spread was wide: transportation 6.2%, other goods and services 4.2%, apparel 3.6%, housing 3.1%, recreation 2.7%, food and beverages 2.6%, education and communication 2.1% and medical care 1.6%.
Inside transportation the spread was wider still. Gasoline rose 27.4% and airline fares 23.4%, while motor vehicle insurance fell 5.1% and used cars and trucks 2.3%. A driver and a non-driver had very different years even though both read the same headline.
Worked example
transportation 6.2%
gasoline +27.4% · airline fares +23.4%
motor vehicle insurance −5.1% · used cars −2.3%
Swapping the weights
Keep the official price changes and replace the official weights with your own, and you have your personal rate. A household spending $4,000 a month — $1,600 housing, $900 transportation, $700 food, $300 medical care and $450 across the rest — lands at 3.57% instead of 3.40%.
The gap looks small until you turn it into money: that basket cost about $138 a month more than a year earlier. A raise below that is a pay cut in everything but name.
Housing is the big lever, and it is measured as rent
Housing is 44% of the basket, and its largest single piece is owners' equivalent rent — what an owner-occupied home would rent for — which alone was 25.9% of the index in July 2026. The CPI does not price mortgage payments at all.
So a homeowner ten years into a fixed-rate mortgage feels less of the shelter increase than the index implies, while a renter whose lease just reset can feel far more. Housing is where personal inflation and official inflation part company most often.
Why the average basket still lands near the headline
Weight the eight group changes by the national weights and you get 3.38% against the published 3.40%. The small difference comes from the weights drifting during the year as relative prices change, and from the index being built from far more detail than eight groups.
That closeness is a useful check: if your own figure is far from the headline, it should be because your spending really is unusual, not because something was entered in the wrong box.
What a personal rate cannot do
Each group is an average of many items, so a household whose transportation spending is almost all fuel saw more than 6.2%. The groups are national, so a city with a tight rental market differs from the average. And the CPI adjusts for quality and package-size changes, which no household-level estimate can replicate.
Use a personal rate for planning and for arguing about a raise, not as a measured index of your own prices. It answers one question well: given what the government measured, how much did my mix of spending cost me?
Common mistakes
Comparing one month's price change with a yearly rate.The headline is a 12-month change; a single month moves far less.Entering a mortgage payment as housing.The CPI measures owner housing as rent, so a fixed mortgage payment understates what the index tracks.Assuming a group's change applies to every item in it.Transportation rose 6.2% while used cars fell 2.3%.Treating the gap as an error in the CPI.A different basket giving a different rate is the index working as designed.