S&P 500 Return Calculator

How this is calculated

Prices. Each month uses the average of that month's daily closes for the S&P Composite, from Robert Shiller's long-run dataset. Dates between monthly points are interpolated, so results can differ slightly from calculators built on daily closing prices. Before 1957 the series is a reconstruction of what the index would have been.

Dividends. The index earns one twelfth of its trailing 12-month dividend each month, paid out monthly. With reinvestment on, each payout buys more of the index at that day's price. With it off, the cash is set aside and counted in the ending value but earns no interest. Dividends from July 2023 onward come from multpl's monthly dividend yield applied to the same prices; July to September 2026 are multpl estimates.

Deposits. The initial investment buys on the start date. Recurring deposits begin one period after the start date and repeat through the end date. A monthly date that doesn't exist, like the 31st in a 30-day month, moves to the month's last day.

Annualized return is money-weighted (an internal rate of return), so it accounts for when each deposit went in. With a single lump sum it equals the compound annual growth rate.

Not included: fund fees, taxes, trading costs and inflation. Past returns don't predict future results, and this is an illustration rather than investment advice.

Sources: Robert Shiller, Yale, via datasets/s-and-p-500; multpl, S&P 500 dividend yield by month.