If I Had Invested in the S&P 500 in Year X

How the calculator works

The calculator takes the S&P 500's total return for each calendar year, which includes dividends reinvested, and applies them one after another to your starting amount. If you add money every month, each year's additions are counted as arriving through the year, so on average they earn half that year's return. The after-inflation figure converts the final value back into the buying power of your starting year using the Consumer Price Index.

Value = amount × (1 + return in year 1) × (1 + return in year 2) × … × (1 + return in the last year)

$10,000 invested at the start of 2000 grew to about $74,000 by the end of 2025, an average of about 8% a year, even though the period began with two crashes: the dot-com bust and the 2008 financial crisis. In 2000 dollars, that is still about $39,500, nearly four times the original buying power.

What the history shows

Over long periods, the S&P 500 has returned roughly 10% a year on average before inflation, but individual years range from gains above 50% to losses of more than 40%. Starting just before a crash, like 1929, 2000 or 2008, made the first years painful, while starting after one, like 2009, gave unusually strong results. Past returns do not predict future ones, but they show why time in the market matters more than timing it.