Calculate your DCA returns, average share price, and total portfolio growth over time.
| Month | Date | Share Price | Invested | Shares Bought | Total Shares | Portfolio Value | Total Return |
|---|
Enter your initial lump-sum investment, recurring contribution amount, and how often you plan to invest. Set your investment period in years, the starting share price, and your expected annual return. The calculator simulates realistic price fluctuations using your volatility setting, then shows your total portfolio value, average cost per share, and a full month-by-month breakdown.
Dollar-cost averaging (DCA) is one of the most effective strategies for long-term investors, yet most people don't realize how dramatically it outperforms trying to time the market. Consider this: if you invested $200 per month into an S&P 500 index fund starting in January 2010, you would have turned roughly $36,000 in contributions into over $120,000 by 2023 — a gain of $84,000.
The real power of DCA is that it removes emotion from investing. When prices drop, your fixed $200 buys more shares. When prices rise, you buy fewer shares but your existing holdings are worth more. Over time, this automatic "buy more when cheap, buy less when expensive" behavior lowers your average cost per share compared to a single lump-sum purchase at the wrong moment.
DCA is ideal for salaried workers contributing to 401(k) or IRA accounts, investors starting with limited capital, and anyone who wants to build wealth without watching the market obsessively. It works especially well in volatile markets — the kind that make lump-sum investors nervous.
Each period, the simulated share price grows by the monthly equivalent of your annual return, with a random variation applied to simulate real-world volatility. The number of shares purchased each period equals:
Shares Purchased = Investment Amount ÷ Share Price That Period
Your average cost per share is then:
Average Cost Per Share = Total Amount Invested ÷ Total Shares Owned
The portfolio value at any point equals Total Shares × Current Share Price. The total return percentage is (Portfolio Value − Total Invested) ÷ Total Invested × 100. Volatility is applied using a seeded random walk so results are reproducible for the same inputs.
Research (including studies by Vanguard) shows lump-sum investing outperforms DCA about 67% of the time in rising markets, because money invested earlier has more time to compound. However, DCA is superior for people who don't have a large lump sum available, and it significantly reduces the risk of investing everything right before a market crash. Most individual investors benefit more from the discipline and risk reduction DCA provides.
Broadly diversified, volatile assets benefit the most from DCA — particularly broad market index funds (S&P 500, total market), ETFs, and growth-oriented stocks. DCA works less well with assets that trend steadily upward without dips, since you'd prefer to buy as early as possible. It's less suitable for stable assets like CDs or money market funds, where price doesn't fluctuate.
DCA actually shines in bear markets. When prices fall 30–50%, your fixed contributions buy significantly more shares. When the market inevitably recovers, those cheap shares generate outsized gains. Historically, investors who maintained DCA through the 2008–2009 financial crisis and the 2020 COVID crash recovered faster and ended up with larger portfolios than those who paused contributions or sold.
Higher volatility (more dramatic price swings) generally benefits DCA investors compared to lump-sum investors. When prices swing wildly, your fixed contributions buy more shares during dips, lowering your average cost. This is called "volatility pumping" — a real mathematical phenomenon where DCA extracts extra return from volatile assets. Steady, low-volatility appreciation is the one scenario where DCA underperforms a single early lump sum.