What Is Inflation?
Inflation is the gradual rise in prices across an economy — equivalently, the gradual fall in what each unit of money buys. At 3% annual inflation, the basket of goods that costs $100 today costs $103 next year; your dollar didn't shrink physically, but its purchasing power did.
It's measured primarily through the Consumer Price Index (CPI) — the tracked cost of a representative basket of goods and services (housing, food, transport, healthcare…). This calculator uses historical CPI data for past comparisons and lets you set any assumed rate for future projections.
Why it matters practically: inflation is the silent tax on cash. Savings that earn less than inflation are losing value while looking safe.
How to Use This Calculator
Historical mode — "what is old money worth now?"
Enter an amount and two years (e.g., $1,000 in 1990 → 2025). The calculator applies actual CPI changes between them and shows the equivalent purchasing power, total inflation percentage, and average annual rate.
Forward mode — "what will today's money buy later?"
Enter an amount, an assumed annual rate (the long-run US average is ~3%; recent years have varied widely), and a number of years. You'll see the future cost of today's basket — or equivalently, today's value of future money.
Historical: ValueB = Amount × (CPIB ÷ CPIA)
Worked Examples
Historical: $1,000 in 1995 → today
CPI roughly doubled over that span, so ~$1,000 of 1995 spending power requires about $2,050–2,100 today — meaning a dollar kept in cash since 1995 buys less than half of what it did.
Forward: $50,000 salary, 3% inflation, 20 years
| Question | Math | Answer |
|---|---|---|
| Cost of today's $50k lifestyle in 20 yrs | 50,000 × 1.0320 | ≈ $90,306 |
| Value of $50k received in 20 yrs, in today's terms | 50,000 ÷ 1.0320 | ≈ $27,684 |
Both directions matter: retirement targets must grow with the first row, while promised future sums must be discounted with the second.
The Rule of 70 and Inflation Milestones
Estimate how long prices take to double: divide 70 by the inflation rate.
| Rate | Prices double in ≈ | Cash loses half its power in ≈ |
|---|---|---|
| 2% | 35 years | 35 years |
| 3% | 23 years | 23 years |
| 5% | 14 years | 14 years |
| 8% | 9 years | 9 years |
Even "low" inflation is consequential across a career: at 3%, a 40-year retirement plan spans nearly two full price-doublings.
Nominal vs Real: The Distinction That Changes Everything
Nominal values are raw dollars; real values are inflation-adjusted. Every long-term financial claim should be sanity-checked in real terms:
- A 5% raise during 4% inflation is a ~1% real raise.
- A bond yielding 4% during 3% inflation earns ~1% real.
- "$1M by retirement" in 30 years ≈ $412k of today's purchasing power at 3%.
This is why long-term savings generally need growth assets: cash and low-yield accounts have real returns near or below zero, while diversified portfolios have historically cleared inflation by several points. Model the growth side with the Investment Calculator.
Protecting Your Money From Inflation
- Keep only working cash liquid — an emergency fund, in the highest-yield safe account you can find.
- Invest long-term money in assets that outgrow inflation — broad equity funds have the strongest long-run record.
- Consider inflation-protected bonds (e.g., TIPS-style instruments) for the conservative slice.
- Negotiate pay in real terms — a raise below inflation is a cut; bring the numbers.
- Project retirement in real dollars — build plans on inflation-adjusted returns, not nominal ones (the Retirement Calculator section on inflation covers this).
The Bottom Line
Inflation never sends a bill, which is why most people underestimate it. Run your own numbers above in both directions — what your past money became, and what your future money must become — and let the results calibrate every savings target, salary negotiation, and investment decision you make this year.