Project how an initial investment plus monthly contributions grows over time at a given return.
Give it a starting amount, a monthly contribution, an expected annual return, and a time horizon. It compounds the balance monthly and returns the projected future value, the total you contributed, the growth attributable to returns, and overall ROI. It models the pattern most people actually invest with — a lump sum plus steady monthly additions — rather than a one-off deposit.
Start with $10,000, add $500/month, assume 7% annually for 20 years. You contribute $130,000 in total, but the projected future value is roughly $301,000 — around $171,000 of it pure growth. Run the same inputs over 30 years and future value jumps past $690,000: the final decade generates more growth than the first two combined, which is compounding in a nutshell.
Not directly. Enter a nominal return to get future dollars, or enter an inflation-adjusted return (e.g. 7% instead of 10%) to read the result in today's purchasing power — the second approach is usually more useful for planning.
Contributions are compounded monthly using the standard future-value-of-annuity formula, equivalent to investing at the end of each month. Contributing at the start of the month would produce a very slightly higher result.
Use the account's quoted APY — typically 3–5% in recent years for high-yield accounts, and far less for standard ones. Reserve 7%+ assumptions for diversified long-term stock investments.