What happens if you invest $500 a month
Investing $500 a month at an 8% average annual return grows to about $745,180 after 30 years, from just $180,000 of your own money. Here is the full picture.
Growth table: $500 a month
| Time | You put in | At 6% | At 8% | At 10% |
|---|---|---|---|---|
| 5 years | $30,000 | $34,885 | $36,738 | $38,719 |
| 10 years | $60,000 | $81,940 | $91,473 | $102,422 |
| 15 years | $90,000 | $145,409 | $173,019 | $207,235 |
| 20 years | $120,000 | $231,020 | $294,510 | $379,684 |
| 25 years | $150,000 | $346,497 | $475,513 | $663,417 |
| 30 years | $180,000 | $502,258 | $745,180 | $1,130,244 |
| 35 years | $210,000 | $712,355 | $1,146,941 | $1,898,319 |
| 40 years | $240,000 | $995,745 | $1,745,504 | $3,162,040 |
Monthly contributions at month end, returns compounded monthly, no taxes or fees. Starting balance $0.
How long until you're a millionaire?
Investing $500 a month from scratch, you would reach $1,000,000 in about 40.1 years at 6%, 33.4 years at 8%, or 28.9 years at 10%.
Why the last decade matters most
Look at the 8% column. Going from 30 to 40 years adds more than the first 20 years combined. That's compounding: in later years, growth on your existing balance far exceeds your contributions. Starting earlier beats investing more later.
Want to add a starting balance or raise your contribution each year? Try the compound interest calculator with $500/month pre-filled.
Where to invest $500 a month
For most people, a low-cost, broadly diversified index fund (a total US market or S&P 500 fund, often paired with an international fund) inside a tax-advantaged account is the simplest place to start. Many brokers let you schedule automatic monthly investments, including fractional shares.
Common questions
How much will $500 a month be worth in 20 years?
About $294,510 at an 8% annual return, $231,020 at 6%, or $379,684 at 10%. You would have contributed $120,000.
Is an 8% return realistic?
The US stock market has returned about 10% a year nominally over the long run, but with big swings and decade-long flat stretches. 6–8% is a common planning assumption for a stock-heavy portfolio.