Buying Power Calculator
See how inflation erodes what a dollar buys. Enter an amount in dollars, an expected annual inflation rate in percent, and a number of years — you get the amount's future buying power, the sum needed to match today's power, and the percent lost.
Example: with Amount ($) 1000 · Annual inflation rate (%) 3 · Years from now 20 → Buying power then (in today's dollars): $553.68.
- Needed to match today's buying power$1,806.11
- Purchasing power change44.6% of purchasing power lost
Computed by the calculator below using its default values. Change any input to see your own numbers.
Future buying power = amount ÷ (1 + inflation)^years. At 3%, prices roughly double every 24 years (rule of 72), halving what cash buys.
How inflation compounds against cash
Buying power falls by division, not subtraction. If prices rise 3% a year, a dollar buys 1 ÷ 1.03 of what it did last year — and after 20 years, 1 ÷ 1.03²⁰, about 55 cents on the dollar. That is why $1,000 held as cash for 20 years at 3% inflation ends up buying what $553.68 buys today, and why you would need $1,806.11 then to live like $1,000 now.
The rule of 72 gives quick intuition: divide 72 by the inflation rate to estimate how long prices take to double. At 3%, roughly 24 years; at 8%, about 9 years — which is why $100 through nine years of 8% inflation keeps only about $50 of its power. The U.S. CPI has averaged near 3% over the long run, but stretches like 2021-2022 ran far hotter, compressing decades of erosion into months.
Using this for planning
Two practical moves follow from the math. First, state long-term goals in real terms: a retirement income of '$60,000 in today's dollars' 25 years out means targeting about $125,000 nominal at 3% inflation. Second, compare the erosion rate to what your cash earns — savings yielding less than inflation lose power every year, which is the case for keeping long-horizon money in assets with real (after-inflation) returns.
How it’s calculated
Future buying power = amount ÷ (1 + r)^y; amount needed to match today = amount × (1 + r)^y; power lost = (1 − 1/(1+r)^y) × 100. r is the assumed annual inflation rate compounded yearly; results are shown in dollars and cents.
Assumes one constant inflation rate for the whole span — actual CPI varies year to year, and your personal inflation rate depends on what you buy.
What $1,000 in cash is worth after 3% annual inflation
| Years | Buying power (today's $) |
|---|---|
| 10 | $744.09 |
| 20 | $553.68 |
| 30 | $411.99 |
| 40 | $306.56 |
Computed with 1,000 ÷ 1.03^years; rounded to cents.
Common mistakes
- Multiplying the loss linearly — 3% for 20 years is not a 60% loss; compounding makes it 44.6%.
- Discounting with subtraction (amount × (1 − 0.03 × years)) instead of dividing by (1.03)^years.
- Using the average of past inflation for a short horizon — next year's rate can differ a lot from the 30-year mean.
- Ignoring that wages and yields can also rise with inflation; cash under the mattress takes the full hit, invested money may not.
Frequently asked questions
What is the buying power formula?
Future buying power = amount ÷ (1 + inflation rate)^years. $1,000 at 3% for 20 years: 1,000 ÷ 1.03²⁰ = $553.68 in today's purchasing power.
Is losing buying power the same as losing money?
Your nominal balance does not shrink — $1,000 stays $1,000. What shrinks is what it buys. That is the common confusion: inflation is a tax on purchasing power, not on the printed number.
What inflation rate should I assume?
U.S. CPI inflation has averaged roughly 3% over the past century and the Federal Reserve targets 2%. Use 2-3% for long-range planning, and test higher rates to see your downside.
How do I keep up with inflation?
Hold assets with expected real returns — stocks, TIPS, I bonds, or savings yields above the inflation rate. The 'needed to match' figure tells you the nominal target your money must reach.