Dollar-Cost Averaging and Compound Growth: Assumptions and Risks

Investor.gov defines dollar-cost averaging as investing equal amounts at regular intervals through market ups and downs. A fixed dollar payment buys more units at lower prices and fewer at higher prices. The resulting average purchase cost is not proof that the final sale price will be higher.

For example, three hypothetical $100 purchases at prices of $10, $5 and $20 buy 10, 20 and 5 shares: 35 shares for $300, with an average cost of about $8.57 per share. If all 35 shares are later worth $5 each, the holding is worth $175 before costs. Regular purchasing has not prevented a loss.

All growth examples below are hypothetical: a constant 7% nominal annual rate compounded monthly, end-of-month contributions, no withdrawals, and no fees, taxes or inflation adjustment. They are nominal future dollars, not forecasts or today’s purchasing power.

Under those growth assumptions, $500 per month for 30 years gives $609,985.50, including $180,000 contributed. At $400 per month, it gives $487,988.40, including $144,000 contributed. The calculator grows cash flows at a constant rate; it does not simulate share-price paths or demonstrate that DCA outperforms another strategy.

Contribution timing matters. A deposit made at the end of December has no growth before that year-end observation in the month-end model. Do not give every contribution a full year of growth. Beginning-of-month contributions use a different convention.

Investing from each paycheck is different from deliberately holding an already available lump sum in cash and deploying it gradually. A fair comparison must specify when funds become available, cash returns, investment prices, costs and risk exposure. This article does not promise a universal historical win rate for either approach.

Automation can help maintain a schedule, but it does not eliminate emotional decisions or losses. A falling price can reflect lasting deterioration rather than a temporary discount. Affordability, emergency needs, concentration, fees and investment suitability still matter. No fixed percentage of salary is appropriate for every household.

To reproduce the growth illustration, enter principal 0, contribution 500, rate 7, monthly compounding, end-of-month timing and 30 years. Keep fees, tax and inflation outside this reference. For an actual investing plan, separate the contribution schedule from assumptions about future market returns and review both over time.

Correction, October 29, 2026: examples, assumptions, FAQs and visuals were reviewed together. Unsupported current statistics and promises were removed. The stated calculations use independent high-precision references.