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Future Inflation and Purchasing Power

Why the same dollars may buy less later — and how to read a simple future inflation projection.

By Greg, Editor at Finance Maxx. Published · Updated

Purchasing power is what a dollar can buy. If prices rise, cash sitting still buys fewer goods. That is not a reason to spend everything today. It is a reason to notice that a 0% savings account is slowly losing real value, and that a “$50,000 in 20 years” goal is not the same basket as $50,000 today.

Two useful views

  1. Erosion — today’s amount in future purchasing power (what it still “feels like” later)
  2. Future cost — dollars needed later for the same basket of goods

The future inflation calculator projects both from amount today, an annual inflation rate, and years ahead.

If inflation is i per year for n years:

  • Future cost ≈ amount × (1 + i)^n
  • Purchasing power of cash left idle ≈ amount ÷ (1 + i)^n

Worked example

$50,000 today, 3% inflation, 20 years:

  • (1.03)^20 ≈ 1.806
  • Same basket later ≈ $90,300
  • $50,000 left in a 0% account feels like about $27,700 in today’s goods

A steady 2–3% rate is a common long-run planning assumption, not a forecast. The 1970s and 2021–2023 were not 3%. Use 2%, 3%, and 5% as a range, not a single sacred number.

What this is not

It is not CPI, not a Fed model, and not a reason to assume stocks return 10% forever. Pair it with savings & investment growth only if you put a return you actually believe in the growth tool. A 10% growth assumption next to 3% inflation is a 7% real claim. Say that out loud before you plan a retirement date on it.

Social Security COLAs, rent, and college costs do not all move at the same i. This page is one rate on one pile of dollars.

Try it

Goals denominated in today’s dollars

A “$1 million retirement” headline is today’s shopping basket only if you inflate it. At 3% for 25 years, $1 million later buys about what $478,000 buys now. Either raise the nominal target or plan in real dollars (the FIRE calculator uses a real return for that reason). Mixing a nominal growth rate with a real spend target is how plans look easier than they are.

Enter an amount that matters to you, 10–20 years ahead, and 3% annual inflation. Expand the breakdown for future cost, purchasing power lost, and cumulative inflation. Then change the rate. The sensitivity is the lesson.