Investment Calculator
Project the future value of a starting amount plus regular monthly contributions at an assumed return — with a clear split between what you put in and what growth added.
Investment growth
Example: $10,000 to start, $500/mo at 7% for 30 years → about $691,150.
Contributions versus growth
In the worked example — $10,000 to start plus $500 a month at a 7% return for 30 years — the balance reaches about $691,150. Of that, only $190,000 is money you contributed; the larger part, $501,150, is investment growth. That crossover — where growth overtakes contributions — is the whole point of investing early, and it's computed here by the same tested engine as the calculator above.
Time in the market
The single most powerful input is the number of years. Because returns compound, the last decade of a 30-year horizon adds far more than the first, so the balance curve bends sharply upward at the end. Regular contributions amplify it: steady monthly investing (dollar-cost averaging) keeps adding fuel to the compounding without requiring you to time the market.
Use a return you can defend
Small changes to the rate move the ending balance a lot over long horizons, so it's tempting to assume the best. Resist it: subtract investment fees from your assumed return, and run a conservative case alongside the optimistic one. A plan that still works at 5% is far sturdier than one that needs 9% every year to succeed.
Frequently asked questions
What return should I assume?
For a diversified stock portfolio, long-run historical returns have averaged roughly 7% a year after inflation (around 10% before), but returns are volatile and the future is not the past. A more conservative 5–6% is a reasonable planning figure for a mixed portfolio. Always sanity-check a plan against a lower return.
Does this account for inflation?
The projection is in nominal dollars — it does not discount for inflation. To see roughly what the balance is worth in today’s money, use a real (after-inflation) return: if you assume 7% growth and 3% inflation, enter about 4% to see inflation-adjusted purchasing power.
End-of-month or start-of-month contributions?
The timing option controls whether each contribution is invested at the end of the month (the default) or the beginning. Contributing at the start of the period gives each dollar one extra month of growth, so the beginning option produces a slightly higher balance.
What about fees and taxes?
Neither is modeled here. Investment fees reduce your effective return — subtract them from the rate you enter — and taxes depend on the account type. In a tax-advantaged account (401(k), IRA) growth is sheltered; in a taxable brokerage account, gains and dividends may be taxed along the way.
Not financial advice: a general educational estimate in nominal dollars that assumes a constant return and excludes fees and taxes. Markets are volatile and returns are not guaranteed. Values are processed locally in your browser and never transmitted. See the methodology page.