Compound Interest Calculator
Watch a small monthly contribution grow into something serious.
$622,788
Contributed
$185,000
Growth
$437,788
Growth multiple
3.37×
Starting 0 years earlier would have grown to
About
Compound growth is hard to feel without seeing it. Set a starting amount, monthly contribution, return rate, and time horizon. The chart shows how much of the final number is your contributions vs. growth on growth. Slide the 'started X years earlier' control to see how much time matters.
How to use
- Enter starting balance, monthly contribution, expected annual return, and years.
- See the final value, total contributed, and growth-on-growth.
- Drag the 'years earlier' slider to see what starting sooner would have done.
FAQ
What return rate should I use?+
Long-run average for a US stock index is around 7% real (after inflation) or 10% nominal. Use 7% for purchasing-power planning, 10% for headline numbers. Bond-heavy portfolios are closer to 4 to 5%.
Is the compounding monthly or annual?+
Monthly. Contributions are added at the end of each month and compounded at the monthly equivalent of your annual rate.