Investing
Dollar-Cost Averaging Explained, With Real Numbers
By MarketsBench · Published · 3 min read
Dollar-cost averaging (DCA) means investing a fixed amount at regular intervals, whatever the price. Because the amount is fixed, it buys more units when the price is low and fewer when it is high.
It is often sold as a way to beat the market. It is better understood as a way to remove timing decisions, with a cost in some markets and a benefit in others.
How the average cost works out
$100 a month for five months, at prices of $50, $40, $25, $40 and $50:
| Month | Price | Units bought |
|---|---|---|
| 1 | $50 | 2.0 |
| 2 | $40 | 2.5 |
| 3 | $25 | 4.0 |
| 4 | $40 | 2.5 |
| 5 | $50 | 2.0 |
| Total | 13.0 |
$500 bought 13 units, an average cost of $38.46 per unit. The average of the five prices is $41.00. DCA's average cost is always at or below the simple average price, because the cheap months buy more units.
At the final price of $50 the position is worth $650, a 30% gain, even though the price ended exactly where it started.
DCA versus investing everything at once
The same $500 invested in different markets:
| Prices over 5 months | DCA ends at | Lump sum in month 1 ends at |
|---|---|---|
| $50, $40, $25, $40, $50 (dip, recovery) | $650.00 | $500.00 |
| $40, $45, $50, $55, $60 (steady rise) | $612.42 | $750.00 |
| $60, $55, $50, $45, $40 (steady fall) | $408.28 | $333.33 |
The rising and falling markets use the same five prices in opposite order, so DCA buys at the same $48.99 average cost in both. The outcome still depends entirely on the path:
- In a rising market, DCA lags: the later buys happen at higher prices.
- In a falling market, DCA loses less: it keeps cash back from the first, most expensive price.
- Through a dip and recovery, DCA wins clearly: it buys the most units at the bottom.
Broad markets have tended to rise over long periods, which is why studies of past returns usually find that investing a lump sum straight away beat DCA more often than not. DCA's real advantage is behavioural: it removes the decision of when to start, and it makes falling prices feel like an opportunity rather than a threat.
DCA is not the same as averaging down
Averaging down means adding to a losing trade to lower the average entry. It looks similar, but the intent is different:
- DCA is a plan made in advance: fixed amount, fixed schedule, long horizon, usually a broad investment.
- Averaging down is a decision made mid-trade, usually on a single position that is going against you, and it increases risk on the trade that is already wrong.
From $40 after buying at $50 and $40, a position needs a 12.5% rise just to reach its $45 average cost. Know that number before adding.
Making DCA work
- Automate it. The benefit comes from not deciding each month. A manual plan quietly turns into market timing.
- Watch the fees. A fixed commission on small, frequent buys can eat a large share of the amount. Subtract per-order costs from each buy.
- Pick a long enough horizon. Five buys is an illustration. DCA is meant to run for years, where the averaging has room to work.