What is the Consumer Price Index (CPI)?
The Consumer Price Index (CPI) tracks what city households pay for goods and services. BLS sets the 1982 – 84 average at 100, so an index of 110 means prices are 10% higher. We use the same series as the BLS calculator (CPI-U, all items, not seasonally adjusted). A year average swings less than a single month. October 2025 has no figure: BLS couldn't collect prices during the federal shutdown.
Source BLS · Consumer Price Index questions and answers ↗BLS · CPI Inflation Calculator ↗
How to calculate inflation
Here it is with your numbers:
- Consumer Price Index for 1990 (year average): 130.7. For September 2026: 336.940.
- Same buying power: $100.00 × 336.940 ÷ 130.7 = $257.80.
- Change in prices: (336.940 − 130.7) ÷ 130.7 × 100 = 157.8%.
- Over 36.2 years that’s 2.6% a year on average.
It means you’d need $257.80 in September 2026 to buy what $100.00 bought in 1990.
Source BLS · CPI-U, U.S. city average, all items (CUUR0000SA0) ↗
What $100.00 from 1990 is worth in other years
| Year | Same buying power |
|---|---|
| 1913 | $7.57 |
| 1920 | $15.30 |
| 1930 | $12.78 |
| 1940 | $10.71 |
| 1950 | $18.44 |
| 1960 | $22.65 |
| 1970 | $29.69 |
| 1980 | $63.05 |
| 1990 | $100.00 |
| 2000 | $131.75 |
| 2010 | $166.84 |
| 2020 | $198.02 |
| 2025 | $246.32 |
| September 2026 (latest) | $257.80 |
FAQs
How much is $1 in 1970 worth today?
Using the 1970 year average, $1 in 1970 had the same buying power as $8.68 in September 2026, the latest month published.
Source BLS · CPI-U, U.S. city average, all items (CUUR0000SA0) ↗
What is the formula for inflation?
Take the change in the Consumer Price Index and divide it by the starting index: (later CPI − earlier CPI) ÷ earlier CPI × 100. From 112.500 to 121.500 is a rise of 8.0%.
How much has CPI increased in the last 12 months?
From September 2025 to September 2026 the Consumer Price Index rose from 324.800 to 336.940: 3.7%.
Source BLS · CPI-U, U.S. city average, all items (CUUR0000SA0) ↗
What does 5% inflation rate mean?
Prices rose 5% over the year: what cost $100 a year ago costs about $105 now.
Sources
- BLS: CPI Inflation Calculator
- BLS: CPI-U, U.S. city average, all items (CUUR0000SA0)
- BLS: Consumer Price Index questions and answers