Estimate what an amount will cost in the future, or how much today's money will actually buy later, using an assumed average annual inflation rate.
Both numbers come from the same compounding formula run in opposite directions: FV = amount × (1 + rate)^years for the future cost, and RV = amount ÷ (1 + rate)^years for what a fixed amount is worth later once inflation has chipped away at it. This is deliberately a simplified constant-rate model, the same shape as compound interest math, just pointed at prices instead of an investment balance.
$10,000 today, 20 years out, assumed rate 3%. What costs $10,000 now costs $18,061.11 in 20 years. Run the same $10,000 forward as idle cash instead of a price tag and it buys $5,536.76 worth of today's goods after 20 years, roughly 55 cents on the dollar.
Actual inflation is published as an index, like the US CPI-U, that moves unevenly year to year and differs by country and spending category. Getting that history right means pulling it from the agency that publishes it, not estimating it from a spreadsheet formula. This tool sticks to one rate you pick and compounds it consistently, a planning tool, not a historical record.
Not official economic data, and not financial advice. Actual inflation varies by year, country, and spending category. For historical figures, check your country's statistics agency (e.g. the US Bureau of Labor Statistics for CPI-U) rather than this calculator.