// learn · Data & tools
Compound interest calculator
Enter a starting amount, what you add each month, an expected annual return and a time horizon. The future value, and how much of it is your own contributions vs compounded interest, is computed live in your browser. Nothing is sent anywhere.
Future value: €0
Contributions vs interest
Two things build the final number: the money you put in yourself (contributions) and the return that money earns on top (interest). Early on almost all the balance is your own money. Over enough years the interest, which itself starts earning interest, overtakes it, that crossover is what "compounding" really means.
Why the return number matters so much
Small differences in annual return compound into large differences over decades. A percentage point of extra return, or a percentage point of fees, changes the end result far more than it looks like it should. Use a realistic long-run figure, not last year's best case.
Educational tool, not financial advice. Returns are assumed constant and are never guaranteed, real markets swing. Interest is compounded monthly with contributions added at month end.