Prices have a doubling clock too
Inflation is growth in prices. If prices rise 3% a year, the same Rule of 72 math applies: they double in about 24 years (exactly 23.45). The flip side is buying power: after about 23 years at 3%, $100 buys what $50.67 buys today. Nothing was taken from your account; the dollars just stretch less.
Three tools on one page
Buying power shows what an amount will be worth in today's dollars after a number of years at a steady inflation rate: amount ÷ (1 + inflation)^years. Implied rate works backward from two prices. The Bureau of Labor Statistics consumer price index (CPI-U) roughly doubled from January 1990 to January 2020: $100 of 1990 stuff cost about $202.49. That works out to about 2.38% a year. Running in place compares your growth with inflation; if your pay or savings grow 3% and prices grow 3%, your real change is zero.
Real vs nominal
"Nominal" means the dollar number you see. "Real" means after inflation. The exact real change is (1 + growth) ÷ (1 + inflation) − 1. Subtracting one rate from the other is a quick approximation that works well for small rates. When a calculator shows a big future balance, it's nominal unless it says otherwise.
Inflation isn't steady
Real inflation moves around. It ran near 2% for much of the 2010s and jumped to about 8% in 2022. At 8%, prices double in about 9 years. The page uses one steady rate to show the mechanics; it isn't a forecast. For real month-by-month CPI comparisons, the BLS CPI Inflation Calculator is the source to check.
Why it matters for other calculators
Inflation is the reason a savings rate below it loses buying power, and why long-term growth examples often look better in nominal dollars than in today's dollars. On the compound interest page you can add an inflation rate to see both.
Sources
Last reviewed: Sep 28, 2026