$100 a month in the S&P 500 since 1984
Investing $100 every month in an S&P 500 index fund from January 1984 to Sep 2026 added up to $51,300. With dividends reinvested, it would be worth about $1,065,390.
Real monthly S&P 500 data, updated monthly. How we calculate$100 a month into the S&P 500 since Jan 1984 is worth
You would have put in $51,300 over 513 monthly buys. At the worst point, around Mar 2009, the balance was down 48% from its high, and the plan kept buying.
If you had invested the whole $51,300 in Jan 1984, it would be worth $5,999,771. S&P 500 monthly average prices, dividends reinvested (recent months use the last reported dividend, Jun 2023). Data through Sep 2026. One buy per month at that month's average price; no fees or taxes. Past returns do not predict future returns.
The result
That is 513 monthly buys. The balance ended at 20.8× the money put in, a money-weighted return of 11.3% a year. Without reinvesting dividends it would be $558,138, so dividends added $507,252.
Prices rose along the way, so the deposits are worth more in today's money than their face value: $51,300 of deposits equals about $95,474 in today's dollars. Even measured that way, the plan ended 11.2× ahead.
The hardest stretch: the balance fell 48% from its high around Mar 2009, during the 2008 financial crisis. Someone who kept buying through that drop bought shares cheaply, which is a large part of the final number.
| After | Put in | Worth |
|---|---|---|
| 5 years (1988) | $6,000 | $8,458 |
| 10 years (1993) | $12,000 | $24,797 |
| 20 years (2003) | $24,000 | $85,708 |
| 30 years (2013) | $36,000 | $194,815 |
| 40 years (2023) | $48,000 | $628,485 |
| Now (Sep 2026) | $51,300 | $1,065,390 |
How the balance grew, with dividends reinvested. No fees or taxes.
Try other amounts and years
Common questions
How much is $100 a month in the S&P 500 since 1984 worth today?
About $1,065,390 as of Sep 2026, from $51,300 invested, with dividends reinvested and no fees or taxes.
What was the yearly return?
11.3% a year, measured as a money-weighted return that accounts for when each monthly deposit went in.
What was the worst moment?
A 48% fall from the previous high around Mar 2009, during the 2008 financial crisis. The plan only reached today's value because the buying continued.
Will the next 43 years be the same?
Nobody knows. Past returns do not predict future returns, and the S&P 500 has had decade-long stretches with little gain.
Based on the S&P 500 monthly average level with dividends reinvested (an index fund before its small fee). Educational estimates, not investment advice. Past returns do not predict future returns.
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