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CPI Inflation Calculator from Two Index Values

What do these figures come to once the work is shown?

Dollar amount restated with the ratio of two CPI index values, the percent change, purchasing power and annualized inflation, per the BLS method.

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  • Free, no sign-up
Your figures
Example figuresIllustrative only. Type over them with your own.
Equivalent amount in the later period
$505
Earlier amount restated in later-period dollars
Percent change in the CPI
1.02%
Index point change
2.43
Drawn to one scale
Percent change in the CPI1.02%
Purchasing power of an earlier dollar98.99%
Annualized inflation1.02%
All results
MeasureResult
Equivalent amount in the later period$505
Percent change in the CPI1.02%
Index point change2.43
Purchasing power of an earlier dollar98.99%
Annualized inflation1.02%
How this was worked out
Work shownrecomputed as you type
Equivalent amount = amount x (later CPI / earlier CPI)
Percent change = (later CPI - earlier CPI) / earlier CPI x 100
Purchasing power = earlier CPI / later CPI
Annualized = (later CPI / earlier CPI)^(1 / years) - 1

Illustrative arithmetic on the figures you enter. Check the result against your firm's methodology before relying on it.

The formulas

  • Equivalent amount = amount x (later CPI / earlier CPI)
  • Percent change = (later CPI - earlier CPI) / earlier CPI x 100
  • Purchasing power = earlier CPI / later CPI
  • Annualized = (later CPI / earlier CPI)^(1 / years) - 1

How it works

The Bureau of Labor Statistics shows how to restate a dollar amount between two periods: multiply it by the ratio of the later index to the earlier index. The BLS example uses May 2015 (237.805) and May 2016 (240.236): $500 in May 2015 equals $505.11 in May 2016. The example in this tool reproduces it.

Both index values must use the same reference base, such as 1982-84=100. For a 12-month change, use the same month in both years. Annual averages and monthly values answer different questions, so do not mix them. The BLS online calculator uses the CPI-U, U.S. city average, all items, not seasonally adjusted series. BLS could not collect October 2025 CPI survey data because of a lapse in appropriations, and its online calculator does not compute results that use October 2025.

Illustrative figures only. Check the result against your firm's methodology before relying on it.

Common questions

Where do I find the index values?

From the BLS CPI database. Pick one series, such as CPI-U U.S. city average, and use it for both periods.

Why is the percent change not the sum of monthly changes?

Percent changes compound. BLS notes that an over-the-year change is not equal to the sum of the monthly changes.

Can I use this for a contract escalation clause?

Yes, if the clause names the series and months. Use exactly the series and base the contract names.

Sources

Runs in your browser. The figures you type are not sent to CORAA or stored. Check the result against your firm's methodology before relying on it.

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