Compound Interest Calculator
Enter a starting amount, a monthly contribution, a rate of return, and a number of years to see exactly how compound growth adds up — plotted out year by year.
Final balance$–
You contributed$–
Growth from returns$–
Assumes a steady annual return compounded monthly — real returns vary year to year, so treat this as a long-term estimate.
Why the chart curves upward
Early on, most of your balance comes from what you've contributed. Over time, the returns you've already earned start earning their own returns — that's compounding, and it's why the line bends upward instead of climbing in a straight line.
Want to see this applied to a specific goal? Try the 401(k) Growth Calculator or read Index Funds, Explained for where this kind of growth actually comes from.