What the calculator is really doing
Money from different years is not directly comparable, because the same dollar buys less as prices rise. A price index fixes this by tracking the cost of a fixed basket of goods over time, so amounts can be restated in the money of any year.
That is the whole calculation. The only inputs beyond your amount are the two index values, which the page keeps in a built-in table of the US CPI-U.
A worked example
Take $100 from the year 2000 and carry it forward to 2025:
| CPI in 2000 | 172.2 |
|---|---|
| CPI in 2025 | 321.9 |
| $100 in 2000 equals | $186.96 in 2025 |
The number does not mean the $100 grew. It means that keeping the same buying power you had in 2000 would take $186.96 in 2025 — and, read the other way, that cash left under a mattress lost nearly half its purchasing power over those 25 years.
What an index can and cannot tell you
The CPI is a national average of one basket, published as annual figures here. It is excellent for comparing historical amounts and terrible as a description of your personal cost of living, which depends on what you actually buy. Use it to translate past prices into today's money, not to settle how much inflation you specifically have felt.
Frequently asked questions
How does an inflation calculator work?
It scales an amount by the ratio of a price index between two years. The formula is value_now = amount × CPI_now / CPI_then. Using the US CPI-U, $100 from the year 2000 (index 172.2) is worth $100 × 321.9 / 172.2 = $186.96 in 2025 — the same buying power, expressed in each year's dollars.
Which price index does this use?
The US CPI-U, the Consumer Price Index for All Urban Consumers, published by the Bureau of Labor Statistics with base years 1982–84 set to 100. It tracks a representative basket of goods and services for city households, and it is the series most commonly meant by 'the inflation rate' in the United States.
What years are covered?
The built-in table runs from 1990 to 2025. The values are annual averages, so a within-year figure will differ slightly from a specific month. The table is baked into the page and refreshed once a year rather than pulled live, which keeps the tool fast and dependency-free.
What is the difference between CPI and the inflation rate?
CPI is the index level; the inflation rate is how fast it changes. If CPI goes from 300 to 309 in a year, that is a 3% inflation rate. This calculator works directly with the index levels, which is more accurate over long spans than chaining one annual rate after another.
Why does official inflation sometimes feel too low?
Because the CPI measures an average basket, and your own spending is not average. If a big share of your budget goes to categories rising faster than the basket — rent or healthcare in many years — your personal inflation runs hotter than the headline number. The index is a fair average, not a description of any one household.