Compound Interest Calculator
See how your money grows over time. Adjust the inputs below and watch compound interest work its magic.
| Year | Balance | Contributions | Interest Earned |
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How compound interest really works.
Compound interest is what happens when your returns start generating their own returns. You earn interest not just on what you originally invested, but also on all the interest that has already accumulated. Over time, this creates an exponential growth curve — often called the snowball effect.
The earlier you start, the more powerful this effect becomes. Even small monthly contributions can grow into substantial wealth over decades because time is the most critical variable in the equation. This is why starting at 25 instead of 35 can mean hundreds of thousands of dollars in difference.
A quick mental shortcut: the Rule of 72. Divide 72 by your annual return rate, and you get the approximate number of years it takes to double your money. At 7% returns, your money doubles roughly every 10.3 years.