Watch compounding do the heavy lifting
Enter a starting amount, a monthly contribution, an expected annual return, and a time horizon. You get the final balance, how much of it you contributed, how much is growth — and a year-by-year table showing the curve bend upward.
Frequently asked questions
How is interest compounded here?
Monthly: each month the balance grows by one-twelfth of the annual rate, then your contribution is added. Monthly compounding closely matches how brokerage and savings balances actually accrue.
What rate should I assume?
Historically, broad stock index funds have returned about 7% annually after inflation over long periods; savings accounts much less. Try a range — the point of the table is seeing how sensitive the outcome is.
Why does the growth accelerate in later years?
That's compounding: interest earns interest. In early years contributions dominate; after a decade or two, growth on the existing balance usually outpaces what you're adding.