See the power of compound interest. Calculate how your investments will grow with regular contributions over time.
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Compound interest is what happens when you earn interest on your interest. Instead of growing in a straight line, your money grows exponentially — slowly at first, then faster and faster over time. Albert Einstein reportedly called it the eighth wonder of the world, and the math backs that up.
This calculator lets you adjust four key variables: your starting amount, monthly contribution, annual return rate, and time horizon. The interactive chart shows you exactly how your money splits between what you contributed and what compound interest earned for you. For most long-term investors, the interest eventually exceeds the total amount they contributed.
For example, investing $500 per month at an 8% average annual return for 30 years results in a total of about $745,000 — even though you only contributed $180,000 out of pocket. The remaining $565,000 came from compound interest. This is why starting early matters so much: time is the most powerful variable in this equation.