Method / assumptions / examples
How this calculation works
The result is deterministic: the same measurements always return the same estimate. Here is the relationship and where real-world results can differ.
Formula
Equivalent dollars = amount × target-year CPI ÷ start-year CPI
The ratio uses the U.S. Bureau of Labor Statistics CPI-U All Items, U.S. city average, not seasonally adjusted series (CUUR0000SA0). Historical years use the BLS annual average; the current year uses the latest published monthly observation when an annual average is not yet available. The percentage change is the CPI ratio minus one.
Worked example
Examples
If the CPI rises from 172.2 to 310.0, $100 at the earlier price level has about the same broad purchasing power as $180.02 at the later level.
A CPI ratio of 1.25 represents a 25% increase in the indexed consumer-price level between the selected years.
Common mistakes
What to check before using the result
- Compare values from the same CPI series and frequency. Annual averages and individual monthly readings answer slightly different questions.
- Treat a current-year result as provisional: it uses the latest available month and can change as additional observations are published.
- Treat the result as an estimate of broad consumer purchasing power, not the change in price of one product or in one city.
- Inflation adjustment is not an investment-return calculation and does not include taxes, interest, dividends, or transaction costs.
FAQ
Frequently asked questions
What does CPI measure?
This tool uses the official BLS CPI-U All Items, U.S. city average, not seasonally adjusted series. It tracks average price change for a defined basket and is not a price index for every household.
How is the current year handled?
Completed historical years use annual-average CPI. Until the current year has an annual average, the tool uses the latest published monthly CPI and identifies that source period.
Does the result mean every item became that much more expensive?
No. Categories and regions move at different rates. The result describes the selected broad index, not any single item.
Can I use this as an investment return calculator?
No. It compares price levels. Investment performance also depends on cash flows, fees, taxes, and the timing of gains and losses.