Compound interest calculator
How much you would have made investing every month in a real stock or ETF, dividends included, in euros or in its own currency. Or project your contributions with the return you choose.
Examples
How it works
With a real stock or ETF, the calculator replays history month by month: every contribution buys shares at that month's real close, dividends are collected for the shares you held and, if you choose so, reinvested. The result is your money's annual return (IRR) and what you would have today.
The projection applies compound interest month by month: final value = capital × (1 + r)^t, plus each contribution growing from the month it goes in.
To estimate what a stock is worth today, try the fair value calculator.
Frequently asked questions
What is compound interest?
Earning a return on what you have already earned. If €1,000 returns 7% a year, you make €70 in year one, but in year two the 7% applies to €1,070. With monthly contributions and many years, that snowball ends up weighing more than the money you put in.
How does it calculate what I would have made?
With the stock's real monthly closes. Each contribution buys shares at that month's close; dividends are paid on the shares you held and, if you reinvest them, buy more shares at that month's close. In euros, each contribution is converted at that month's exchange rate and the final value at today's. No fees or taxes are deducted, except the withholding you choose.
What is the IRR and why doesn't it match the stock's return?
The IRR is the annual return on your money taking into account when you invested it. The stock's return is that of a single purchase at the start. With monthly contributions much of your money was invested for less time, so the IRR can be higher or lower depending on how the stock did after each contribution.
Why is the result different in euros than in dollars?
Because the exchange rate counts too. If the dollar weakens against the euro while you hold US shares, you make less in euros than in dollars, and vice versa. Before 2004 there is no reliable monthly exchange rate: for those years the calculation is in the stock's currency.
What return should I use for the projection?
A prudent one. The S&P 500 has returned close to 10% a year on average over the very long run (in dollars, with dividends, before inflation), with much worse decades. For a diversified portfolio, 5-7% is a reasonable assumption. Try several: over 30 years the difference is huge.
Does it include fees and taxes?
No. Every purchase has its fee and the final sale is taxed. To compare fees, see the broker comparison.
Calculation tool using public data. Not investment advice. Past performance does not guarantee future results.