Compound Interest Calculator
Project savings or investment growth with compound interest and monthly contributions, including a year-by-year balance table.
Processed locally in your browser — nothing is uploaded.
Whole years, up to 100.
Enter a principal, rate, and number of years to see growth.
About Compound Interest Calculator
Start with a principal, add an optional monthly contribution, pick an annual rate and compounding frequency (daily, monthly, quarterly, or annually), and see the final balance after any number of years. Results split the ending balance into what you put in versus what interest earned, with a year-by-year table so you can watch the curve bend.
Contributions use standard future-value-of-annuity math: they're converted to a per-period amount and added at the end of each compounding period, so the annual amount you save stays the same whichever frequency you pick.
Common uses
- Project what a monthly savings habit is worth in 10 or 30 years
- Compare daily vs annual compounding at the same nominal rate
- Show how much of a future balance is interest rather than deposits
Example
Input
$0 start · $100/mo · 6% compounded monthly · 10 years
Output
$16,387.93 — $12,000 contributed, $4,387.93 interest
Limitations
- Uses a constant nominal annual rate; real investment returns vary year to year, and taxes and fees are not modeled.