Enter your starting amount, monthly contribution, interest rate, and years — see exactly how your money grows and how much of it is pure interest working for you.
Compound interest is interest calculated on both your initial principal and the interest you've already earned. Unlike simple interest — which only earns on the original amount — compound interest grows exponentially over time. The longer you leave your money invested, the more powerful this effect becomes.
Enter your starting amount, how much you'll add each month, your expected annual interest rate, how many years you'll invest, and how often interest compounds. The calculator shows your final balance, how much of it is interest, and a visual chart of your money growing year by year.
Even small monthly contributions dramatically accelerate your results. Adding just $100/month to a $1,000 starting balance at 7% over 20 years turns into over $52,000 — compared to only $3,870 without any contributions. Consistency beats timing every time.
Start as early as possible — time is the most powerful variable in compound interest. Automate monthly contributions so you invest consistently. Choose accounts with higher APY and more frequent compounding. And resist the urge to withdraw — every dollar you pull out loses all its future compounding potential.