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Weight the official price changes by how you actually spend, across the eight groups of the US consumer price index, to get your own inflation rate for the year to August 2026 and compare it with the official figure.
Best for: Why prices feel higher than the CPI, Budgeting for next year, Salary negotiations, Teaching how the CPI is weighted
Updated September 2026 · Estimates only, not financial advice.
The official 3.4% is an average of eight groups
The Bureau of Labor Statistics splits the consumer price index into eight major groups and weights each by its share of the national basket. In December 2025 housing was 44.5% of the basket, transportation 16.3%, food and beverages 14.5%, medical care 8.4%, education and communication 5.8%, recreation 5.1%, other goods and services 2.9% and apparel 2.4%.
rate = Σ share(i) × change(i)
Weighted this way, the group price changes to August 2026 give 3.38%, within two hundredths of the official 3.40%; the small gap comes from the weights drifting with relative prices during the year. Your rate uses the same price changes and your own weights instead.
A renter who drives a lot runs at 3.57%, not 3.40%
Take $4,000 a month: $1,600 on housing, $900 on transportation, $700 on food, $300 on medical care and $450 across the other four groups. Transportation is 22.5% of this budget against 16.3% of the national one, and it rose 6.16%, so the household’s rate comes out at 3.57%.
The same basket cost about $138 a month less a year earlier. That is the practical number: it is what a raise has to cover before it is a raise at all.
$4,000 a month
40% × 3.13% + 22.5% × 6.16% + 17.5% × 2.61% + …
= 3.57%
$4,000 − $4,000 ÷ 1.0357 = $138
Transportation rose 6.2%, on gasoline up 27.4%
Transportation was the fastest-rising group in the year to August 2026. Inside it, gasoline was up 27.4% and airline fares 23.4%, while motor vehicle insurance fell 5.1% and used cars and trucks 2.3%, according to the BLS release.
That spread is why commuters felt this year’s inflation more than people who rarely drive. Medical care, at 1.6%, was the slowest group, and education and communication, at 2.1%, the next.
Housing is 44% of the basket, and most of it is rent
Housing prices rose 3.1% over the year and shelter, its largest part, 3.0%. The CPI measures an owner’s housing cost as the rent the home would fetch, owners’ equivalent rent, which alone was 25.9% of the index in July 2026.
That makes the CPI a renter-shaped measure. A homeowner with a fixed-rate mortgage pays the same each month however rents move, so entering the mortgage payment here, rather than a market rent, usually gives a lower personal rate than the official one.
What eight groups can and cannot tell you
Each group is itself an average. Transportation mixes gasoline, cars, insurance and fares, so a household that spends its transportation budget almost entirely on fuel saw more than 6.2%. The groups also cover the whole country; prices in a particular city can differ.
The official index updates its weights each year from household spending surveys and adjusts for quality changes and smaller package sizes. This calculator keeps the BLS price changes and only swaps the weights, which is the part that differs most from one household to another.
Limitations
Eight broad groups average over many items; a household that mostly buys gasoline inside transportation will see more than the group change.
US national averages only; prices differ by region.
Frequently Asked Questions
What was US inflation in August 2026?
The CPI-U was 3.4% higher than a year earlier: 334.980 in August 2026 against 323.976 in August 2025, according to the Bureau of Labor Statistics.
Why is my inflation different from the CPI?
The CPI weights price changes by the national average basket. If you spend more than average on something that rose faster, such as transportation at 6.2%, your rate is higher; spend more on medical care at 1.6% and it is lower.
Does the CPI include my mortgage payment?
No. The CPI prices owner-occupied housing as the rent a home would earn, owners’ equivalent rent, which was 25.9% of the index in July 2026. A homeowner with a fixed-rate mortgage does not pay that rent.
Sources & References
Figures on this page are checked against primary, authoritative sources. Links open in a new tab.
Results are estimates based on the figures you enter and standard formulas. Rates, fees, taxes, and lender terms vary and change over time, so confirm important numbers with your lender or a qualified professional. This is educational information, not financial advice.
Personal Inflation vs the CPI: Why Your Prices Rose Faster or Slower
The CPI weights price changes by the national basket. Swap in your own spending and the rate moves — worked through the August 2026 figures, group by group.
Published a personal inflation rate calculator: the eight CPI-U major groups with BLS December 2025 weights and 12-month changes to August 2026, weighted by the reader's own spending, against the official 3.4%.
Group indexes from the BLS API; all-items and apparel changes checked against the published August 2026 Table 1.
Added an automated formula suite with BLS published figures as the outside authority.
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