Historical and Custom Inflation Calculator
Compare U.S. monthly CPI-U from January 2016 to August 2026, enter matching custom CPI values, or model a constant-rate scenario with transparent assumptions.
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Calculation references: BLS CPI-U historical monthly table · Sources checked 2026-10-01
Formula
Historical equivalent = amount × ending CPI ÷ starting CPI. Constant-rate scenario = amount × (1 + annual rate ÷ 100)^(ending year − starting year).
Worked example
If a matched price index increases from 100 to 125, an initial 100 corresponds to 125 in the ending period, a 25% index increase. This example illustrates the ratio, not a reported historical series.
What the result means
Historical monthly CPI and user-entered scenarios are distinct. The result compares purchasing power in one currency; it does not perform currency exchange, predict future inflation, or describe every household’s costs.
How to Use Inflation Calculator
Choose the calculation mode
Select bundled U.S. monthly CPI, custom index values, or a hypothetical rate scenario.
Enter amount and periods
Choose available months or provide matching index values for your country.
Review equivalent purchasing power
See the index-ratio equivalent amount and cumulative change.
Key Features & Benefits
Measured historical comparison
The U.S. mode uses a dated BLS CPI-U snapshot rather than assuming one constant historical rate.
Missing data stays missing
October 2025 is unavailable; future periods are not extrapolated.
Frequently Asked Questions
Which country has bundled historical data?
The United States has a monthly CPI-U snapshot from January 2016 through August 2026. Other countries require matching official index values you supply.
Why can I not select October 2025?
BLS lists the observation as unavailable due to the lapse in appropriations; the tool does not interpolate it.
Is the custom rate a forecast?
No. It is a hypothetical constant-rate assumption, clearly separated from measured historical CPI.
Key terms
- CPI-U
- BLS all-items consumer price index for urban consumers, U.S. city average, not seasonally adjusted. Household spending can differ from this index.