Dollar-Cost Averaging (DCA) Calculator
Dollar-cost averaging (DCA) means investing a fixed amount at regular intervals — $500/month, for example — regardless of what the market is doing. When prices drop, you buy more shares; when they rise, you buy fewer. Over time, this averages your purchase price and removes the impossible task of timing the market.
The DCA vs lump sum debate is one of investing's most studied questions. Vanguard's research across 21 markets found that lump sum investing beats DCA about 68% of the time — because markets go up more often than they go down. But DCA significantly reduces the risk of investing right before a crash, and for many investors, the psychological comfort is worth the statistical cost. This calculator uses Monte Carlo simulation to show you both outcomes.
Investing $500/month for 10 years grows to $91,473 at 8% average return ($31,473 growth on $60,000 contributed). A $60,000 lump sum invested today would grow to $129,535. Historically, lump sum beats DCA ~90% of the time — but DCA reduces timing risk.
DCA inputs
Fixed amount you invest each month
Same total as DCA contributions for fair comparison
S&P 500: ~10% nominal, ~7% real
S&P 500 historical: ~18%. Higher = more uncertainty.
DCA vs Lump Sum
DCA Final Balance
$91,473
$60,000 contributed + $31,473 growth (1.52x)
Lump Sum Final Balance
$129,535
$60,000 invested + $69,535 growth (2.16x)
Lump sum wins 90% of the time
Based on 500 Monte Carlo simulations. Markets tend to go up, so money invested earlier has more time to compound. But DCA protects against the worst-case scenario of investing right before a crash.
DCA growth over time
| Year | Contributed | Balance | Growth |
|---|---|---|---|
| 1 | $6,000 | $6,225 | $225 |
| 2 | $12,000 | $12,967 | $967 |
| 3 | $18,000 | $20,268 | $2,268 |
| 4 | $24,000 | $28,175 | $4,175 |
| 5 | $30,000 | $36,738 | $6,738 |
| 6 | $36,000 | $46,013 | $10,013 |
| 7 | $42,000 | $56,057 | $14,057 |
| 8 | $48,000 | $66,934 | $18,934 |
| 9 | $54,000 | $78,715 | $24,715 |
| 10 | $60,000 | $91,473 | $31,473 |
How to use this calculator
Monthly investment — The fixed amount you invest each month via DCA. This should be an amount you can consistently afford regardless of market conditions. Common amounts: $200–$2,000/month depending on income.
Lump sum comparison — The total amount you'd invest upfront for comparison. For a fair comparison, set this equal to your total DCA contributions (monthly investment × years × 12). The calculator shows which strategy wins.
Expected annual return — Your assumed average annual return. S&P 500 historical average: ~10% nominal, ~7% after inflation. Use 7% for real (inflation-adjusted) projections.
Investment period — How long you plan to invest. Longer periods favor lump sum more strongly because the money has more time to compound. For DCA, 6–12 months is the typical averaging period.
Market volatility — Annual standard deviation of returns. S&P 500 historical: ~18%. Higher volatility means more uncertainty and a wider range of outcomes in the Monte Carlo simulation.
Real-world examples
$10K windfall: DCA over 6 months vs lump sum
You receive a $10K bonus. DCA: invest $1,667/month for 6 months. Lump sum: invest $10K today. Historically, lump sum wins ~68% of the time by an average of ~2% more. But if the market drops 20% in month 2, DCA saves you ~$1,600. The question: can you stomach a potential short-term loss?
$500/month salary investing (automatic DCA)
Most people already DCA through their 401(k) or automatic investments. $500/month at 8% for 30 years = ~$745K on $180K contributed (4.1x multiple). This is the most practical form of DCA — you're investing from cash flow, not choosing between DCA and lump sum.
$100K inheritance in a volatile market
A large windfall makes the DCA vs lump sum decision harder. DCA over 12 months: invest ~$8,333/month. If the market drops 30% during that year, DCA saves ~$20K. If the market rises 15%, DCA costs you ~$8K in missed gains. At 18% volatility, Monte Carlo shows lump sum wins ~65% of the time but DCA has a better worst-case outcome.
Formula & Methodology
DCA growth formula
- r = Annual expected return (decimal)
- PMT = Monthly investment amount
Lump sum growth formula
- PV = Initial lump sum investment
- r = Annual return (decimal)
- n = Number of years
Monte Carlo simulation
The calculator runs 500 Monte Carlo simulations using a geometric Brownian motion model: monthly returns are drawn from a normal distribution with mean = annual return / 12 and standard deviation = annual volatility / √12. This produces a range of possible outcomes and estimates the probability of lump sum outperforming DCA.
Assumptions & limitations
- Returns are normally distributed. Real market returns have fat tails (more extreme events).
- Does not account for taxes, transaction costs, or bid-ask spreads.
- Volatility is assumed constant. Real volatility clusters (high-vol periods follow high-vol periods).
- DCA comparison assumes you hold cash earning 0% while averaging in. In practice, cash earns some interest.