Inflation and purchasing power calculator
Project a future equivalent price and purchasing-power loss using a constant annual inflation rate.
This choice applies to every calculator; amounts are not converted.
Constant-rate projection only; this is not an economic forecast.
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How does this tool work?
This projection illustrates purchasing-power erosion when prices rise at a constant annual rate. It helps reason in future money without pretending to forecast real inflation.
The calculator compounds the selected annual inflation rate on the starting amount. Each projected year therefore builds on the previous year’s price level. Future equivalent cost shows how much would be needed to purchase the same basket later, while future purchasing power shows the opposite effect on a nominal amount that does not increase. This is a mathematical constant-rate scenario, not an economic forecast.
How to use this tool
Enter the current amount
Provide the price, budget or balance whose purchasing power you want to examine.
Choose the rate
Enter an assumed annual inflation percentage for the scenario.
Set the duration
Choose the number of years to project future cost and purchasing power.
Good to know
A constant rate is an assumption
The tool applies the same rate every year. Real inflation varies a lot from year to year: use a long-run average for horizons of ten years or more, and several scenarios (2%, 3%, 4%) to see how sensitive the result is.
Your inflation is not the average index
The consumer price index reflects an average basket. Depending on what you spend on (rent, energy, healthcare, food), your personal inflation can be much higher or lower: for a specific expense, enter the rate for that item.
Inflation projection formulas
The tool applies a constant annual inflation rate, compounded year after year.
Future equivalent cost
Future equivalent cost = Current amount × (1 + Annual inflation ÷ 100)^Duration
What the same basket will cost later.
Future purchasing power
Future purchasing power = Current amount ÷ (1 + Annual inflation ÷ 100)^Duration
Value, in today’s money, of an amount kept without any return.
Cumulative inflation
Cumulative inflation = ((1 + Annual inflation ÷ 100)^Duration − 1) × 100
Total price increase over the whole duration.
- M
- Current amount
- i
- Annual inflation (%)
- n
- Duration (years)
- C
- Future equivalent cost
- P
- Future purchasing power
- I
- Cumulative inflation (%)
Constant-rate projection: actual inflation changes every year.
Use cases
Long-term budgeting
Estimate the scale of a future expense if prices rise at the annual rate you selected.
Savings target
See how much a future amount may need to grow to preserve comparable purchasing power.
Scenario comparison
Try several inflation assumptions to understand how small annual differences accumulate over time.
Examples
€1,000 with 2% inflation over 10 years
1,000 × 1.02¹⁰ = €1,218.99: that is what the same purchase will cost, and €1,000 will only be worth €820.35 in today’s money.
Input
Current amount: €1,000; Annual inflation: 2%; Duration: 10 yearsResult
Future equivalent cost: €1,218.99; Future purchasing power: €820.35; Cumulative inflation: 21.9%Tips and best practices
- Compare several rates instead of relying on one scenario.
- Treat the result as a projection rather than a forecast.
- Keep the same currency when comparing amounts.
Sources and references
- Insee — Key facts about inflation in France (opens in a new tab)Page in French
- ECB — What is inflation? (opens in a new tab)Page in English
Frequently asked questions
Is this a forecast?
No. The calculator simply applies the constant rate you enter and does not predict actual future prices, monetary policy or economic conditions.
Why does purchasing power fall?
When prices rise while a nominal amount stays unchanged, that amount can buy fewer goods and services, so its real purchasing power decreases.
What formula is used?
Future equivalent cost uses annual compounding: amount × (1 + rate)^duration. Purchasing power applies the inverse effect for the same scenario.
Can average inflation predict a specific product price?
No. Individual prices can move differently from the average index used for the projection.
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