Final Balance
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After compound growth
Total Contributed
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Your out-of-pocket total
Interest Earned
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Money made by investing
Balance over time
How compound interest works
Compound interest means you earn interest not just on your initial deposit, but also on all the interest you've already earned. Over long time horizons, this compounding effect dramatically accelerates growth — often called "the eighth wonder of the world."
This calculator compounds monthly, which is the most common schedule for savings accounts and investment portfolios. Each month, your interest rate is divided by 12 and applied to your current balance, then your monthly contribution is added.
Tips for maximizing savings growth
- Start as early as possible — time is the most powerful variable in compound growth.
- Increase monthly contributions even slightly; small increases compound significantly over decades.
- A higher interest rate matters more the longer your time horizon.
- Tax-advantaged accounts (401k, IRA, Roth IRA) let compound growth work without annual tax drag.