Compound Interest Calculator
See how your investments grow with compound interest. Calculate final value, total growth, and the power of monthly contributions over time.
Final Value
$343,778
Total Contributed
$130,000
Investment Growth
$213,778
Doubles every ~9.0 yrs
9.0 yrs
AI Insights
AI- 1Your investment grows to $343,778 over 20 years.
- 262.2% of your final portfolio is pure investment growth — not money you put in.
- 3At this return rate, your money doubles roughly every 9.0 years (Rule of 72).
- 4Monthly contributions of $500 are the engine of your long-term wealth. Starting earlier matters more than the amount.
Portfolio Growth Over Time
$10,000
$0$200,000
$500
$0$5,000
8.0%
1.0%15.0%
20 years
1 year50 years
Not financial advice. Estimates only. Consult a qualified adviser.
Why starting early beats starting big
Compound interest is often called the eighth wonder of the world. An investment of $10,000 at 8% becomes $46,610 after 20 years — without adding another penny. Add $500/month and it becomes $305,000.
The Rule of 72: divide 72 by your annual return rate to estimate how many years it takes to double your money. At 8%, your money doubles every 9 years. Starting 10 years earlier gives you one extra doubling — meaning twice as much at retirement.