US inflation calculator

How the formula works

Inflation is measured by a price index. The one used here is the CPI-U — the Consumer Price Index for All Urban Consumers — which the Bureau of Labor Statistics builds by pricing a fixed basket of goods and services each year and expressing the cost against a base period, 1982-84, set to 100. To carry an amount from a start year into an end year's dollars, scale it by the ratio of the two years' index values:

where \(A\) is the original amount. The ratio \(\text{CPI}_{\text{end}}/\text{CPI}_{\text{start}}\) is how much the general price level rose over the span; multiplying the amount by it gives the number of end-year dollars that buys what the original bought. Subtracting 1 from the same ratio gives the cumulative inflation over the whole period.

To turn that cumulative figure into a rate per year, spread it geometrically across the number of years \(t_{\text{end}} - t_{\text{start}}\), exactly as a compound growth rate is recovered from a start and end value:

This is the constant annual inflation rate that, compounded over the span, reproduces the same total change in prices. It is an average: individual years ran hotter or colder than \(\bar r\), and this single number smooths over all of them.

What CPI measures, and what it does not. The CPI tracks the price of one fixed, periodically updated basket meant to represent a typical urban household's spending — food, housing, transport, medical care, and the rest. It is a national average, so it does not reflect any one city or region, where housing especially can diverge sharply. It assumes a basket that does not fully capture substitution — when beef gets dear, people buy chicken, softening the bite in a way a fixed basket understates. And your own inflation depends on what you buy: a renter in a hot market, or a household with heavy medical costs, can run well above or below the headline figure. Treat the result as the broad, national picture, not a reading of your personal budget.

What each input means

Amount — \(A\)

The sum of money to restate. The calculator answers what that many start-year dollars is worth in end-year dollars — the same purchasing power, priced at the later year's prices.

Start year

The year the amount is measured in. Bounded to the CPI-U table, which runs from 1913 — the first year the index exists — through 2024, the latest annual average published. Each year's value is an annual average, not a single month.

End year

The year whose dollars you want the amount expressed in. Choose a later year to see how much more money is needed to keep pace with rising prices; choose an earlier one to run the comparison backward.

A worked example

Take the worksheet's opening numbers: $100 in 1990, expressed in 2024 dollars.

• The CPI-U annual average was 130.7 in 1990 and 313.689 in 2024, so prices rose by a factor of 313.689 / 130.7 = 2.4001×.
• That makes $100 worth $100 × 2.4001 = $240 in 2024 — the same basket, at 2024 prices.
• Cumulative inflation over the 34 years is 2.4001 − 1 = 140.01%, which compounds to an average of \((2.4001)^{1/34} - 1 = 2.61%\) a year.
• Turned around: a 1990 dollar buys only 0.417 of a 2024 dollar's worth, so the original amount's buying power fell by 58.33% over the span.

Assumptions and limits

• The figure is the CPI-U national average. Your city, region and personal basket differ — housing costs in particular vary far more than the headline number.
• Each year is an annual-average index, not a specific month. Month-to month figures within a year can differ from the average used here.
• It is historical, computed from published CPI-U data — not a forecast. It says nothing about what prices will do next year.
• This is arithmetic, not advice. It restates buying power; it does not tell you what to do about it.

Questions people ask

What is the CPI?

The Consumer Price Index measures the average change over time in the prices paid by urban consumers for a fixed basket of goods and services — food, housing, transport, medical care, recreation and more. The Bureau of Labor Statistics prices that basket each month and expresses it against a base period, 1982-84, set to 100. This calculator uses the CPI-U (for All Urban Consumers), annual average. The ratio of two years' index values is how much the general price level changed between them.

Why is my personal inflation different from the CPI?

Because the CPI tracks one national basket, and yours is not that basket. The index weights spending the way a typical urban household does; if you spend more than average on the things rising fastest — rent, childcare, medical care — your own inflation runs hotter, and if you spend less, it runs cooler. Where you live matters too: the CPI is a national average and does not capture a single city's housing market. The headline number is the broad picture, not a reading of your budget.

Is the CPI the same as the cost of living?

Close, but not identical. A true cost-of-living index would account for how people substitute toward cheaper goods when prices shift — buying chicken when beef gets dear — and for quality changes. The CPI uses a mostly fixed basket, which the BLS updates periodically but which cannot fully capture substitution, so it tends to slightly overstate the rise in the cost of maintaining a given standard of living. It is the best broad gauge available, not a perfect one.

What is a “normal” rate of inflation?

The Federal Reserve targets 2% a year, measured on a related index, as consistent with a stable economy. Over the long run US inflation has averaged closer to 3% a year, with stretches well above it — the late 1970s and early 1980s ran into double digits — and occasional years near zero. A single low-single-digit figure is considered healthy; sustained high inflation and outright deflation are both treated as problems.

Does this predict future prices?

No. The calculator uses published historical CPI-U data and does nothing but restate past buying power in another past year's dollars. It has no view on the future and makes no forecast. Future inflation depends on conditions no index of the past can know.