📈 Compound Interest Simulator
Explore how your savings grow over time, distinguish contributions from investment returns, and understand the impact of inflation. All calculations run locally in your browser.
Investment assumptions
Monthly contributions are assumed at the end of each month. The nominal annual rate is compounded at the selected frequency and converted to an equivalent monthly rate.
Projection
Year-by-year breakdown
| Year | Contributed | Nominal value | Real value |
|---|---|---|---|
| Run a projection to see results. | |||
Learn the concepts
What is compound interest?
Returns can themselves earn future returns. For a lump sum, FV = PV × (1 + r/m)^(m×t), where r is the annual nominal rate, m the compounding periods per year, and t the years.
How are monthly contributions modeled?
Each month, the current balance grows by the equivalent monthly return and then the monthly contribution is added. This represents end-of-month payments, not beginning-of-month deposits.
What does inflation-adjusted value mean?
The projected nominal balance is divided by (1 + inflation rate)^years, expressing its purchasing power in today's euros. *The real-gain comparison discounts each historical contribution to today's purchasing-power basis at its payment date; it is a simplified illustrative measure, not an investment performance metric.
Are returns guaranteed?
No. This is a deterministic scenario, not a forecast or investment recommendation. Actual markets fluctuate, and taxes, fees, volatility, and contribution timing can materially change outcomes.