The data
Every number on this site comes from one dataset: the Consumer Price Index for All
Urban Consumers (CPI-U), all items, U.S. city average, not seasonally adjusted,
series CUUR0000SA0, published by the
U.S. Bureau of Labor Statistics. It is the
longest-running official measure of U.S. consumer prices, beginning in 1913, and the
series behind the headline inflation rate reported in the news.
We use the official annual averages (the BLS "M13" rows), not a single month, so a year-to-year comparison reflects the whole year rather than a January or December snapshot. The index base period is 1982–84 = 100: a CPI of 330.724 means prices are roughly 3.3× their early-1980s level.
The formula
The core calculation is a single ratio:
value in year B = amount × ( CPI in year B ÷ CPI in year A )
Example: $100 in 1990, converted to 2026 dollars, is 100 × (330.724 ÷ 130.7) = $253. The cumulative price change over that period is 153.0%.
The average annual inflation rate shown with each result is the geometric mean, the constant yearly rate that would compound to the same total change: (CPIB ÷ CPIA)1/years − 1. For 1990 to 2026 that is 2.61% per year. A simple average of yearly rates would overstate the true compounded change.
A single year's inflation rate is the percentage change in its annual average CPI versus the year before.
Monthly data and the "current" inflation rate
The current inflation rate page and the monthly tables on year pages use the same series at monthly frequency. The headline rate is the 12-month change: this month's index versus the same month a year earlier, not seasonally adjusted. That is the number the BLS leads its releases with and the one news reports cite. It will differ slightly from the calendar-year figures above, which compare annual averages.
Spending-category breakdowns
Conversion pages also show inflation computed against the CPI-U's major category indexes:
food (SAF1), energy (SA0E), housing (SAH), medical
care (SAM), apparel (SAA), transportation (SAT),
recreation (SAR), education & communication (SAE), plus core
CPI (all items less food and energy, SA0L1E). Each uses the same ratio formula
applied to that category's own index. The BLS introduced these indexes at different times
(energy and core in 1957, housing in 1967, recreation and education in 1993), so pages
starting before a category's first year omit it rather than splice unofficial estimates.
How the current year is handled
The BLS publishes a year's annual average only after all twelve months are in. Until then, the current year uses the average of the monthly values published so far. Results involving that year are labeled provisional on the page and are revised with each monthly CPI release (typically mid-month, covering the prior month).
Update process
The dataset is fetched from the BLS Public Data API after each monthly release. Automated checks reject a fetch that has gaps, implausible jumps, or fewer years than the data we already have. A failed update keeps the last good dataset rather than publishing bad numbers. See the data sources & update log for the current dataset's vintage.
Known limitations
- It's a national urban average. CPI-U covers about 93% of the U.S. population, but your personal inflation rate depends on what you buy and where you live. Housing in one metro can move very differently from the national index.
- CPI-U is one measure among several. The Federal Reserve targets the PCE price index, which typically runs a few tenths lower; CPI-W drives Social Security COLAs; Chained CPI adjusts tax brackets. See CPI vs. PCE for how they differ.
- Long comparisons are approximations. The basket, data collection, and quality-adjustment methods have changed many times since 1913. Converting 1913 dollars to today's is faithful to the official index but can't make a 1913 basket of goods truly comparable to a modern one.
- No pre-1913 data. Estimates before the CPI begins rely on academic reconstructions, which we don't mix into the official series.
Citing this site
You're welcome to cite results in articles and research. Attribute them as "InflationCalculator.com, based on BLS CPI-U annual averages" with a link to the specific page. Every conversion has a permanent URL such as /inflation/1990-to-2026/.
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