How the adjustment works
The CPI is a price index: it tracks the cost of a fixed basket of goods and services relative to a base period (1982–84 = 100). If the index is twice as high in one year as in another, prices on average doubled in between. Converting a dollar amount between years is therefore just a ratio of the two index values — no assumed rate is involved, only the measured history.
The formula
Value in year B = amount × CPI(B) / CPI(A) Cumulative inflation = CPI(B) / CPI(A) − 1 Average annual rate = (CPI(B) / CPI(A))^(1 / years) − 1
Worked example
The 2000 annual average CPI-U was 172.2 and the 2025 average was 321.943. So $1,000 in 2000 has the buying power of 1,000 × 321.943 / 172.2 = $1,869.59 in 2025.
Prices rose 87.0% over those 25 years, an average of (321.943 / 172.2)^(1/25) − 1 = 2.53% a year.
Limitations
- CPI-U measures urban consumer prices on average; your own inflation depends on what you buy and where you live.
- The basket and methods have changed over a century (quality adjustment, housing measured by rent equivalence since 1983), so very long comparisons are approximate.
- Values are rounded to the cent; index values are shown as published (three decimals).
Data: U.S. Bureau of Labor Statistics, Consumer Price Index, CPI-U U.S. city average, all items, not seasonally adjusted (series CUUR0000SA0), annual averages 1913–2025 and monthly index for September 2026; retrieved October 30, 2026 via the Federal Reserve Bank of St. Louis, FRED series CPIAUCNS. See also BLS, CPI questions and answers.
Frequently asked questions
Which inflation measure does this use?
The Consumer Price Index for All Urban Consumers (CPI-U), U.S. city average, all items, not seasonally adjusted, published by the U.S. Bureau of Labor Statistics. It is the index most often quoted as "the inflation rate" and covers about 93% of the U.S. population. Data runs from 1913 to September 2026.
Why annual averages instead of a single month?
Prices move during the year, so a year's average index is the fairest single value for "prices in 1990". For the most recent period, the calculator offers the latest monthly index because the current year is not finished.
What does "$100 in 1970 is worth $829 today" mean?
It means a basket of consumer goods and services that cost $100 at 1970 average prices would cost about $829 at 2025 average prices. It does not mean any particular item rose by that much — college tuition, medical care and housing have outpaced the overall CPI, while electronics have fallen.
Why is there no October 2025 figure?
BLS did not collect or publish the October 2025 CPI because of the federal funding lapse. The 2025 annual average used here is the average of the 11 months that were published.
Can I use this for future prices?
No — the CPI only describes the past. To project, pick an assumed inflation rate and use the compound interest calculator with that rate. The long-run U.S. average since 1913 has been a little over 3% a year.
CalcNest results are estimates based on the inputs and assumptions above, not financial, tax or lending advice. A lender's official Loan Estimate or your account statement is the final word.