Inflation Calculator

Historical mode uses the official CPI-U annual averages published by the Bureau of Labor Statistics — the Consumer Price Index for All Urban Consumers, U.S. city average, all items. The conversion is the ratio of the two years’ index values, which is the standard method BLS itself documents.

Annual averages are used rather than a specific month, so results are stable and reproducible. A January-to-January comparison and a December-to-December one give different answers, and neither is "the" inflation rate for a year.

You can compare specific months as well as whole years. A month is a single reading rather than an average, so it carries seasonal movement the annual figures smooth away — useful when you know the actual date, such as a salary in June 1985 or a price on a dated receipt.

Where BLS published no figure for a month, that month is simply not offered. October 2025 is the notable case. Nothing is interpolated from the months on either side, because a number nobody published is not a measurement.

The current year is the one exception. It has no annual average until BLS publishes it the following January, so it uses the latest month published instead — which means "worth today" really is today, and the figure updates each month when BLS releases new data.

Results also break the period down by spending category — food, housing, medical care and the rest — because the headline rate averages things that moved very differently. Each category is measured against itself; the indices use different base periods, so their levels are never compared with each other.

The implied annual rate is the geometric mean over the period, not a simple average — because inflation compounds. The period is measured from the middle of one year to the middle of the other, or to the middle of the latest month.

Projection mode applies a rate you choose going forward, because nobody has future CPI data. It is clearly labeled as an assumption rather than a measurement.