What Happens If You Invest $100 a Month for 20 Years?
Investing $100 a month for 20 years means $24,000 of your own money, which grows to about $46,204 at a 6% average annual return.
| Average annual return | You contribute | Growth | Ending balance |
|---|---|---|---|
| 4% | $24,000 | $12,677 | $36,677 |
| 6% | $24,000 | $22,204 | $46,204 |
| 8% | $24,000 | $34,902 | $58,902 |
What this means for you
A hundred dollars a month can feel too small to matter. The table shows why it isn't. Over 20 years you put in $24,000 of your own money, and at the highest rate in the table, the growth ends up bigger than everything you contributed. That is compound interest: your returns start earning returns of their own.
The three rates are examples, not promises. Investments go up and down, and the stock market has had losing years along the way. That is why this approach works best over long time periods with broad, low cost index funds rather than picking individual stocks.
Time matters more than the amount. Starting with $100 now usually beats waiting to start with more later. One exception: if you carry high interest credit card debt, paying it down first is often a better guaranteed return.
The Investment Guide Coach in The Vault can help you choose an account and set up your first automatic contribution.
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Assumptions and sources
Returns are example averages, compounded monthly, not promises. Real markets rise and fall.
Taxes, fees and inflation are not included.
Last checked: 2026-10-10
For educational purposes only. Not financial advice.