Inflation Calculator – CPI Value of Money Over Time
Compare the purchasing power of a dollar amount across years using historical US inflation, or enter your own annual rate to estimate a future or present equivalent.
Compare the Value of Money Across Years
Inflation Formula
Where:
- \(A\) — amount entered, in dollars
- \(C_s\) and \(C_e\) — annual-average US Consumer Price Index (CPI) values for the start and end years
- \(n\) — number of years between the dates, or the number of years entered in custom mode
- \(r\) — custom average annual inflation rate, in percent
- \(E\) — equivalent amount; \(I\) — cumulative historical inflation; \(R\) — equivalent average annual historical inflation rate; \(L\) — purchasing power lost at the custom rate
Historical mode scales the amount by the ratio of the two annual CPI values. Custom mode applies the same annual rate each year, either compounding forward or discounting a future amount back to today.
Inflation – Calculation Example
Example: The default settings compare $1,000 in 2000 with its equivalent in 2025. The calculator uses annual-average CPI values of 172.2 for 2000 and 321.943 for 2025.
\[E=\$1{,}000\times\frac{321.943}{172.2}=\$1{,}869.59\]
\[I=\left(\frac{321.943}{172.2}-1\right)100\%=86.96\%,\qquad R=\left(\left(\frac{321.943}{172.2}\right)^{1/25}-1\right)100\%\approx2.53\%\]
Result: $1,869.59 in 2025 has approximately the same purchasing power as $1,000 in 2000, according to the annual-average US CPI. Cumulative inflation is 86.96%; the equivalent average annual inflation rate is about 2.53%.
How to use the calculator
- Choose Calculation mode. Select US CPI (historical) to compare two years in the calculator’s dataset, or Custom rate to use an inflation assumption of your own.
- Enter the Amount in dollars. This must be zero or greater.
- For historical mode, enter a Start year and End year from 1913 through 2025. Use whole years, with the start year before the end year. The result is the later-year dollar amount with approximately equivalent purchasing power.
- For custom mode, enter the Average annual inflation rate and Number of years. The rate must be greater than −100%, and the number of years must be a nonnegative whole number.
- In custom mode, set Direction to Future value of today’s money to estimate the later-year amount needed for the same purchasing power. Choose Today’s value of a future amount to express a later-year dollar amount in today’s purchasing power.
Read Equivalent amount as a purchasing-power comparison, not an investment balance. Historical mode also reports Cumulative inflation and Average annual inflation. Custom mode instead reports Purchasing power lost at the rate and duration entered.
What inflation does to the value of money
Inflation is a rise in the general price level over time. When prices rise, a fixed number of dollars typically buys less. The equivalent amount answers a practical question: how many dollars at one point in time would have roughly the same purchasing power as the amount entered at another point?
In historical mode, the calculator compares annual-average values of the US Consumer Price Index for All Urban Consumers (CPI-U). If the end-year index is 50% higher than the start-year index, an amount in the end year must also be 50% higher to match the earlier amount’s CPI-based purchasing power. Cumulative inflation describes the total change across the period; average annual inflation expresses that same total as a constant compounded yearly rate. Actual inflation need not have been the same in each intervening year.
Custom mode is useful for planning rather than looking up a recorded change. For example, an assumed 3% annual inflation rate increases the future cost of an item each year. The reverse calculation discounts a specified future amount into today’s dollars. Purchasing power lost measures how much less a fixed dollar amount would buy after the stated period at the assumed rate; it is not the same percentage as the increase in prices.
Inflation and investment growth are separate. An account balance could grow while its purchasing power falls if returns do not keep up with prices. To project a balance using an interest rate, use the Compound Interest Calculator. You can compare a beginning and ending value as an annualized growth rate with the Compound Annual Growth Rate Calculator.
Assumptions and practical limits
- Historical coverage: The CPI dataset covers 1913–2025. Historical mode compares an earlier year with a later year; it does not accept the same year twice or reverse the year order.
- Annual averages: Each historical index represents a full-year average, so the result does not describe purchasing power on a specific day or in a specific month.
- US-wide measure: CPI-U tracks a broad basket of consumer goods and services. Your expenses, location, or a particular item may change in price at a different rate.
- Constant custom rate: Custom mode compounds one rate for every year. Real inflation varies. Entering a negative rate models deflation and can produce a negative Purchasing power lost result, indicating a gain instead.
- No investment return: Equivalent amounts do not include interest, taxes, fees, or changes in wages. For a savings projection with contributions or returns, use the Savings / Investment Calculator separately.
Frequently Asked Questions
How can I calculate an inflation-adjusted amount by hand?
Look up the annual CPI for each year, divide the later year’s CPI by the earlier year’s CPI, and multiply your original amount by that ratio. For example, if the index rose from 100 to 120, $50 in the earlier year would correspond to $60 in the later year. Use CPI values from the same index series so the comparison is consistent.
What is a normal or good annual inflation rate?
There is no single rate that is normal in every year. The Federal Reserve targets 2% inflation over the longer run, but its target uses the personal consumption expenditures (PCE) price index, not the CPI used for historical results here. A rate for a future estimate is an assumption, not a prediction; consider testing several rates rather than relying on one.
Why can inflation rise by one percentage while purchasing power falls by another?
The percentages use different starting points. If prices rise 25%, something that cost $100 now costs $125. A fixed $100 then buys only 80% as much as before, so its purchasing power has fallen 20%, not 25%. This distinction matters when interpreting the calculator’s custom-rate purchasing-power result.
Can I use this calculator for another currency or to convert dollars into euros?
The historical CPI results apply to US dollars and US consumer prices; they do not describe inflation in another country. Custom mode can model an amount in any currency if you supply an appropriate inflation rate, although the interface labels results with a dollar sign. Neither mode converts currencies: an exchange-rate conversion is a separate calculation.
Why does the calculator show deflation for some historical periods?
Prices did not rise in every period. If the annual-average CPI was lower in the end year than in the start year, the calculated cumulative inflation rate is negative, indicating deflation across those years. An earlier dollar amount would then need fewer dollars in the later year to match its CPI-based purchasing power. That does not mean every individual price fell.
How do I tell whether a pay raise beat inflation?
Compare the percentage change in your pay with the price increase over the same period. For a more precise real pay change, divide your new pay by your old pay, divide that result by the CPI ratio, then subtract one. A 4% raise alongside 3% inflation is a real increase of about 0.97%, not exactly 1%. Taxes and changes in your personal expenses can affect what you actually keep or buy.
Is an inflation-adjusted amount the same as an investment return?
No. An inflation-adjusted amount compares purchasing power, while an investment return measures how an asset or account changed in value. To estimate a real investment return, divide the investment’s growth factor by the inflation factor, then subtract one. This does not account for taxes, fees, or investment risk, so it should not be treated as a forecast or financial advice.