Inflation Calculator
Estimate purchasing power changes with a custom inflation rate or a rough built-in decade-average rate model.
Last reviewed: June 2026Quick Answer
An inflation calculator shows how prices change over time and what money is worth in a different year. At an average 3% annual inflation, $100 today has the buying power of about $134 in ten years — you'd need $134 then to buy what $100 buys now. Enter an amount and a time span above to see the impact.
What this inflation calculator estimates
This calculator estimates how a dollar amount changes when prices rise or fall over time. Enter an amount, a start year, an end year, and an inflation rate. The page returns the adjusted dollar value, purchasing power lost, cumulative inflation, a buying-power sentence, and a year-by-year table for spans up to 30 years.
The default mode is a simplified planning model. When the custom-rate box is unchecked, the calculator uses rough built-in average rates by decade and converts the selected span into a single effective annual rate. When the box is checked, it uses the custom annual rate you enter. This makes the page useful for quick what-if questions, but it is not the same as an official historical CPI conversion.
Formula used on this page
For a forward calculation, the adjusted value is amount x (1 + r)^years, where r is the annual inflation rate as a decimal. Purchasing power is amount / (1 + r)^years, and cumulative inflation is ((1 + r)^years - 1) x 100. For a backward calculation, the adjusted value uses the inverse formula.
The year-by-year table displays the rate used for each row. In custom mode, every row uses the custom rate. In built-in mode, rows display the decade-average rate assigned to that year. Because the headline result uses one effective rate for the whole span, it should be read as an estimate rather than a CPI-index lookup.
Worked default example
With the default inputs, $100 from 2020 to 2026 uses this page's built-in 2020s decade rate of 4.5%. The adjusted value is about $130.23, which means this model says $100 in 2020 would require about $130.23 in 2026 to keep the same buying power. The modeled purchasing power of the original $100 falls to about $76.79, purchasing power lost is about $23.21, and cumulative inflation is about 30.2%.
If you check custom rate and enter 3.0% for the same six-year span, the adjusted value is about $119.41 and cumulative inflation is about 19.4%. That comparison shows why the chosen rate matters. For precise historical results, use an index-based source rather than a rounded long-run assumption.
When to use this page
- Budget planning: Estimate how today's recurring cost might change under a chosen inflation assumption.
- Salary comparisons: Check whether a raise keeps pace with a modeled price increase.
- Savings goals: Convert a future goal into today's buying-power terms.
- Historical context: Build a rough intuition before checking an official CPI-U calculator.
Sources and further reading
For official U.S. historical inflation conversions, use the BLS CPI Inflation Calculator. BLS explains that the CPI calculator uses the Consumer Price Index for All Urban Consumers, U.S. city average, all items, not seasonally adjusted. The BLS inflation and prices overview also explains how CPI data are used to measure price changes.