What Is Inflation?
Inflation is the gradual increase in the price of goods and services over time — which means each dollar buys less than it used to. The U.S. Bureau of Labor Statistics measures inflation through the Consumer Price Index (CPI-U), which tracks the cost of a representative "basket" of goods including food, housing, transportation, medical care, and more.
When you hear that "a dollar in 1980 is worth about $3.70 today," that's a CPI-based comparison: prices have risen roughly 270% since 1980, so you'd need $3.70 now to buy what $1 bought back then.
How the CPI Is Calculated
The BLS surveys prices for thousands of items across hundreds of categories every month. Each category is weighted by how much the average consumer actually spends on it — so housing (about 33% of the index) has a much bigger impact than recreational items. The annual average CPI is the most common benchmark for year-over-year inflation comparisons.
This calculator uses annual average CPI-U values (the most widely cited series). Point-in-time comparisons (e.g., January to January) may differ slightly.
Historical U.S. Inflation Highlights
- 1910s–1920s: WWI drove sharp inflation — prices roughly doubled between 1913 and 1920, followed by a deflationary crash in 1921.
- 1930s: The Great Depression brought deflation — prices actually fell, increasing the real burden of debt.
- 1940s: WWII and postwar demand pushed prices up sharply. Prices rose ~70% between 1940 and 1950.
- 1970s: Oil shocks triggered stagflation. Inflation peaked at 13.5% in 1979 — the worst peacetime inflation in U.S. history.
- 1980s–2010s: Fed Chair Volcker broke inflation with high interest rates. The next three decades saw relatively stable inflation averaging 2–3%.
- 2021–2022: Post-pandemic supply disruptions and stimulus spending drove inflation to a 40-year high of 8.0% in 2022.
The Rule of 72
A quick mental shortcut: divide 72 by the annual inflation rate to estimate how many years it takes for prices to double. At 3% inflation, prices double roughly every 24 years. At 7%, every ~10 years. This also means your money's purchasing power is cut in half over the same period.
Frequently Asked Questions
Why does my grocery bill feel higher than the CPI suggests?
The CPI measures an average basket for an average consumer. Your personal inflation rate depends on what you actually spend money on. If you spend heavily on housing, education, or medical care — all of which have risen faster than overall CPI — your personal inflation experience will be worse than the headline number. Conversely, consumers who buy a lot of electronics or apparel (which have gotten cheaper) may experience less inflation.
What's the difference between CPI-U and PCE?
The Federal Reserve's preferred inflation measure is the PCE (Personal Consumption Expenditures) price index, which adjusts for consumer substitution (if beef gets expensive, people buy chicken). PCE typically runs slightly below CPI-U. This calculator uses CPI-U because it's the most familiar benchmark for everyday comparisons.
Can inflation ever be good?
Mild inflation (around 2%) is generally considered healthy. It encourages spending and investment (rather than hoarding cash), gives the Fed room to cut rates in a recession, and helps borrowers repay fixed-rate debt with cheaper future dollars. The problem arises when inflation runs too hot or becomes unpredictable — then it erodes savings, distorts pricing signals, and hits fixed-income households hardest.