Inflation Calculator

What inflation actually does to your money

Inflation is the steady rise in prices over time, which means a fixed amount of money buys less as the years pass. A dollar isn't worth less in some abstract sense — it simply commands fewer goods. To measure this, economists track the Consumer Price Index (CPI), a basket of typical household purchases priced year after year. This calculator carries U.S. annual-average CPI values from 1913 through 2025 built right in, so it converts the buying power of money between any two of those years instantly, with no API call and nothing sent off your device.

The formula, in one line

The core calculation is a simple ratio of the two years' index values:

adjusted = amount × (CPI[end year] ÷ CPI[start year])

Because the CPI is anchored to a 1982–84 baseline of 100, the absolute numbers don't matter — only their ratio does. The tool also reports cumulative inflation, which is that ratio minus one expressed as a percentage, and buying power lost, computed as (1 − CPI[start] ÷ CPI[end]) × 100. The two percentages answer different questions and are not the same number, which trips people up constantly.

A worked example

Suppose you enter $100, a start year of 1950, and an end year of 2025. The 1950 CPI is 24.1 and the 2025 value is 320.0. The adjusted amount is 100 × (320.0 ÷ 24.1) ≈ $1,327.80 — that's what you'd need today to buy what $100 bought in 1950. Cumulative inflation is (320.0 ÷ 24.1 − 1) × 100 ≈ 1,228%; prices grew more than thirteenfold. Buying power lost is (1 − 24.1 ÷ 320.0) × 100 ≈ 92.5%. Notice the asymmetry: prices rose 1,228%, yet the dollar lost "only" 92.5% of its purchasing power. That's because the two percentages divide by different bases — a 100% price rise halves your money (a 50% loss), not a 100% loss.

Reading the year-by-year table

Below the summary, the tool builds a row for every year in the range showing the value of one start-year dollar and the annual inflation rate. The "value of $1" column is computed as CPI[start] ÷ CPI[year], so it begins at exactly $1.0000 in your start year and shrinks as you move forward. The annual rate is the year-over-year change, color-coded so you can spot the spikes — the early-1980s double-digit years, the 2022 surge to roughly 8%, and the rare deflationary years like 2009 where prices actually fell.

Useful ways to apply it

• Sanity-check old prices. "Gas was 30 cents a gallon" means little until you convert it; the tool turns nostalgia into a fair comparison.
• Evaluate a raise or a pension. If your income rose 20% over a decade but cumulative inflation was 25%, you lost ground in real terms.
• Set salary or contract figures. Adjusting a historical amount forward gives a defensible, data-based number.
• Run it backwards. Set the start year after the end year and the tool shows what a future amount is worth in earlier dollars — handy for understanding the real cost of long-ago events.

Common mistakes and limits

• Confusing the two percentages. Cumulative inflation and buying-power-lost are different views of the same change; don't quote one as the other.
• Expecting your personal inflation. The CPI is a national average basket. If you spend mostly on rent, tuition, or healthcare — categories that have outpaced the index — your lived inflation may be higher.
• Sub-year precision. The data is annual averages, so month-to-month timing within a year isn't captured.
• Region and currency. These figures are U.S. CPI in U.S. dollars; they don't translate directly to other countries.

Because the index is hardcoded, results are identical every time and work offline — turn off your connection and the calculator still runs, confirming nothing leaves your browser.