A dollar today buys less than a dollar did last year โ and much less than a dollar bought a decade ago. That is inflation, and understanding it with numbers is the first step to protecting your savings.
What Is Inflation?
Inflation is the general increase in prices over time. Economists measure it using the Consumer Price Index (CPI) โ a basket of everyday goods and services tracked month by month.
The Inflation Rate Formula
To calculate the inflation rate between two periods:
Inflation Rate = ((CPI Now โ CPI Earlier) รท CPI Earlier) ร 100
Example
If the CPI was 280 in January and 285 in February:
- CPI increase: 285 โ 280 = 5 points
- Inflation rate: (5 รท 280) ร 100 = 1.79% for that month
Annualized, that pace would be about 21% โ which is why month-over-month numbers are reported with care.
How to Calculate the Future Cost of Something
Want to know what something will cost in the future? Use:
Future Cost = Current Cost ร (1 + r)^n
Where r is the annual inflation rate (as a decimal) and n is the number of years.
Example: A $50,000 Car in 10 Years at 3% Inflation
| Year | Value at 3% inflation |
|---|---|
| Now | $50,000 |
| 5 years | $57,964 |
| 10 years | $67,196 |
| 20 years | $90,306 |
The same car you buy for $50,000 today will cost roughly $67,000 in ten years โ even with no feature upgrades.
Real vs Nominal Returns
Your savings account may advertise 4% โ but if inflation is 3%, your real return is only about 1%:
Real Return = ((1 + Nominal Rate) รท (1 + Inflation Rate)) โ 1
That is why cash under the mattress loses value every single year.
Why Even 2% Inflation Matters Over Decades
A small inflation rate compounds into a huge difference:
| Time | Buying power lost from $1,000 at 3% |
|---|---|
| 5 years | โ$141 |
| 10 years | โ$263 |
| 20 years | โ$456 |
| 30 years | โ$590 |
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๐ก Pro Tip: To beat inflation, your long-term investments need to average more than the inflation rate after taxes. Even modest diversification into stocks historically outpaces inflation over 10+ year horizons.
*See exactly how much your money will be worth with our free Inflation Calculator.*
