Future Buying Power Calculator
Inflation reduces purchasing power over time. A dollar today usually buys more than a dollar will buy years from now.
This calculator shows both sides of the arithmetic:
Enter a dollar amount, an assumed annual inflation rate, and a time period to see how inflation changes purchasing power over time.
Annual compounding. See historical CPI reference points below for context — not forecasts.
Trailing geometric average — context for your inflation assumption, not a forecast.
| Period | Canada | U.S. |
|---|---|---|
| Loading CPI data… | ||
Year-by-year rates: Historical Inflation Rates (CPI).
Enter valid inputs to see results.
| Amount today | $— |
|---|---|
| Assumed inflation rate | — |
| Years | — |
| Future dollars required | $— |
| Inflation multiplier | — |
| Purchasing power retained | — |
| Purchasing power lost | — |
| Additional dollars needed | $— |
This calculator uses annual compounding. It does not forecast inflation. It shows the arithmetic result of a user-selected inflation assumption.
The future dollars needed calculation increases today's amount by the assumed inflation rate for each year:
Future dollars = Amount today × (1 + inflation)years
The future buying power calculation discounts a future nominal dollar amount back into today's dollars using the same inflation assumption:
Today's buying power = Future amount ÷ (1 + inflation)years
Purchasing power retained = 1 ÷ inflation multiplier. Purchasing power lost = 1 − purchasing power retained.
That depends on the inflation rate and the time horizon. This calculator shows two related answers: how many future dollars would match today's buying power, and what a future nominal amount would be worth in today's dollars. Both use the same inflation multiplier — one multiplies forward, the other divides back.
For historical CPI-based conversions between specific years, see the Inflation Time Machine.
At the default inputs ($1,000,000, 3% inflation, 20 years), $1,000,000 today would need to grow to about $1,806,111 in nominal dollars to maintain the same buying power. Conversely, $1,000,000 received in 20 years would buy roughly what $553,676 buys today — about 55.4% of today's purchasing power retained.
Change the inflation assumption to see how sensitive the result is. The inflation article walks through why small annual rates compound into large long-run effects.
This calculator does not choose a rate for you. You enter an assumption. The historical CPI reference table shows trailing geometric averages for Canada and the United States over 5, 10, 20, and 50 years — derived from published CPI data, not from forecasts.
For year-by-year historical rates, see Historical Inflation Rates (CPI). For investment growth with inflation adjustment, see the Simple Investment Calculator.
Retirement targets are often stated in today's dollars, but future expenses arrive in future dollars. A lifestyle that costs $10,000 per month today requires more nominal dollars later if prices rise. Plans built only in nominal terms can understate what future spending requires.
This calculator isolates the inflation arithmetic. Portfolio growth, withdrawals, and account rules are modeled separately in tools like the Retirement Withdrawal Calculator.
No. It applies a constant user-entered inflation rate with annual compounding. It shows what the arithmetic produces — not a prediction of future CPI, wages, or personal cost of living.
Historical CPI averages shown on this page describe the past. They are included as reference points only.
Disclaimer: All content on The Long Math — including articles, essays, calculators, tools, or any other material — is provided solely for educational and informational purposes and does not constitute financial, tax, legal, or investment advice. Any results or projections are based on simplified models, assumptions, and user-supplied inputs and may not reflect real-world outcomes. You are responsible for evaluating the accuracy and applicability of the information provided and for conducting your own due diligence. Before making financial decisions, consult a qualified professional.