Compound Interest Calculator
Estimate potential investment growth with regular contributions.
Capital growth
Year-by-year results
| Year | Total contributions | Balance | Estimated gain |
|---|
Illustrative model: constant effective annual return (the portfolio grows by this percentage over 12 months), contributions at month-end. Tax on gains is deducted once at the end on the difference between the final balance and contributions; inflation is constant and converts the result into today’s money. Both fields default to 0. Fees are excluded. Returns are not guaranteed.
How compound interest is calculated
Compound interest means that returns are earned not only on the amount you invested but also on the returns already accumulated. The calculator takes your starting capital, monthly contribution, annual return and period and builds the portfolio month by month. The return is treated as an effective annual rate: over 12 months the capital grows by exactly the percentage you enter, and contributions are made at the end of each month. Tax on gains (optional) is deducted once at the end, and inflation converts the result into today’s money.
Frequently asked questions
Which annual return should I enter?
Nobody knows future returns, so it helps to compare several scenarios, for example 4%, 6% and 8% a year, and see how much the result changes. Historical index fund returns do not guarantee future ones.
What does “in today’s money” mean?
It is the final amount adjusted for the purchasing power of today’s euro. With 2% inflation a year, €100 in 20 years will buy roughly what €67 buys today.
Are fund fees included?
No. Subtract the fund’s ongoing charge (TER) from the return yourself: for example, with a 7% return and a 0.2% TER enter 6.8%.
This information is general and educational and is not investment advice.