Calculatrice d'investissement progressif

Dollar Cost Averaging Calculator

Dollar cost averaging (DCA) means investing a fixed dollar amount on a regular schedule — weekly, biweekly, or monthly — regardless of what the market is doing. Because you buy more shares when prices are low and fewer when prices are high, your average cost per share over time is lower than the average price during that period. This mechanical approach removes the temptation to time the market, keeps you invested through volatility, and builds wealth systematically even when you do not have a lump sum to deploy. This calculator shows your total contributions, total growth, and final portfolio value based on your chosen amount, frequency, return rate, and time horizon.

How Dollar Cost Averaging Works

DCA projects your portfolio using the future value of an annuity formula:

FV = PMT x [(1 + r)^n - 1] / r

Where PMT is your fixed periodic investment, r is the return per period (annual return divided by the number of investment periods per year), and n is the total number of investment periods. Because each contribution buys shares at a different price, the average cost per share is the harmonic mean of prices over the period — always lower than the arithmetic mean. In practice, a $500/month investor buying at $50, $40, and $60 per share ends up with 30.83 shares at an average cost of $48.65, while the average price over those three purchases was $50.00.

Worked Examples

Scenario 1 — Young investor, $300/month for 30 years: Alex invests $300/month starting at age 25 in an S&P 500 index fund with an 8% average annual return. Total contributions: $108,000. Final portfolio value at age 55: approximately $447,108. Investment growth (money made without contributing): $339,108. That is more than three dollars earned for every dollar put in.

Scenario 2 — Mid-career accelerator, $1,000/month for 20 years: Diane starts investing $1,000/month at 40 into a diversified equity fund at 7% return. Total contributions: $240,000. Final portfolio value at 60: approximately $521,228. She contributed $240,000 and the market added $281,228 — slightly more than she put in herself.

Scenario 3 — High earner, $2,500/month for 25 years: Marcus invests $2,500/month at 7% return for 25 years. Total contributions: $750,000. Final portfolio value: approximately $2,027,675. Investment growth: $1,277,675. The final decade of his 25-year plan generates more growth than his first 15 years combined, illustrating the exponential back-loading of long-term compounding.

DCA Growth Reference Table

When to Use This Calculator

• You want to know how much your automatic 401(k) contribution will grow by retirement based on your current contribution rate and employer match
• You are deciding how much to increase your monthly brokerage account contribution and want to see the 20-year dollar impact of adding $100, $200, or $500 more per month
• You received a raise and are evaluating whether to increase monthly investments by the full raise amount, half, or a fixed dollar figure
• You are comparing DCA with a lump sum investment — see what happens if you invest $60,000 now versus $1,000/month over 60 months at the same return rate
• You want to stress-test your plan at different return rates (6%, 8%, 10%) to understand the outcome range over a 25-30 year horizon

Common Mistakes to Avoid

1. Stopping contributions during market downturns. The worst time to pause DCA is during a correction or bear market, because those are the months you buy shares at the deepest discounts. An investor who skips $1,000/month contributions for 12 months during a bear market and resumes when the market recovers misses both the cheap shares and the recovery gains. At 7% annual return, 12 skipped monthly contributions of $1,000 costs approximately $48,000 in final portfolio value over a 25-year horizon.

2. Investing in high-fee funds. An actively managed fund charging 1.0% annually versus a broad index fund charging 0.05% takes 0.95% off your return every year. On a $500/month DCA plan at 7% gross for 30 years, a 1.0% fee reduces final balance from $566,765 to $494,239 — a $72,526 drag for no additional return.

3. Setting a fixed dollar amount and never increasing it. Inflation erodes the real value of your contribution over time. $500/month invested in 2010 had 50% more real purchasing power than the same $500/month in 2026. Increasing contributions by 2-3% annually to keep pace with inflation and ideally by more with each raise is the difference between reaching your goal and falling short.

4. Treating DCA as a timing strategy rather than a discipline strategy. DCA does not guarantee you buy at lower prices than a lump sum — in a steadily rising market, lump sum outperforms DCA about two-thirds of the time. DCA’s primary value is behavioral: it keeps you consistently invested regardless of headlines, volatility, or your own anxiety about entry price.

Current Context for 2026

• S&P 500 historical return (50-year average): approximately 10% nominal; 7% real after inflation
• 2026 401(k) contribution limit: $23,500/year ($31,000 with catch-up contributions for ages 50+), or roughly $1,958/month ($2,583 with catch-up)
• 2026 IRA contribution limit: $7,000/year ($8,000 age 50+), or $583/month ($667 with catch-up)
• Common DCA vehicles: 401(k) payroll deductions, IRA automatic transfers, taxable brokerage account auto-invest features, Roth IRA monthly contributions
• Low-cost index funds: Vanguard VTSAX/VTI, Fidelity FZROX, Schwab SCHB — all under 0.05% expense ratio; ideal for long-term DCA
• Market conditions 2026: Major indices near all-time highs after the 2022-2023 correction recovery; DCA remains appropriate regardless of market level because the next correction date is unknowable

Tips

1. Automate on payday, not at month-end. Set automatic transfers from your checking account to occur the day after your paycheck clears. Investing before you see the money eliminates the decision — and the temptation to spend it first. This single habit is responsible for more long-term wealth creation than any other.
2. Increase your DCA amount by 1% of salary every year. A $75,000 salary with a 1% increase means adding $62.50/month to your investment. Over 30 years at 7%, that incremental $62.50/month (in year one) compounds to roughly $75,000 in extra portfolio value.
3. Never pause during a bear market. Market corrections are when DCA delivers its most tangible benefit. If you stop at -20%, you miss the cheapest purchase prices of the cycle. Keep investing; the portfolio math rewards the investor who does not blink.
4. Use broad index funds, not sector bets. A DCA strategy only works if your underlying investment recovers from every drawdown. A single company can go bankrupt; the S&P 500 has never permanently declined. DCA into the whole market, not individual stocks.
5. Model contribution increases before you get the raise. Before each annual review, run this calculator with your current contribution, your expected contribution after a raise, and the difference over 20 years. Seeing $120,000 in extra portfolio value from a $200/month increase makes the case for prioritizing the raise toward savings.
6. Track your average cost per share annually. In a brokerage account, your custodian shows your average cost basis. Comparing it to the current share price tells you how well the DCA smoothing has worked. In a strong bull market, the average cost will lag the current price — which is normal and expected.

Related Calculations

• Compound Interest Calculator — model a lump sum investment to compare against your DCA projection and see which approach yields more at your specific return rate
• Roth IRA Calculator — apply DCA mechanics within a Roth IRA to see how regular contributions grow completely tax-free by retirement
• 401(k) Calculator — model DCA with employer matching contributions factored in, which effectively boosts your return by 50-100% on matched dollars
• Savings Calculator — compare DCA in equities against consistent deposits into a high-yield savings account to evaluate risk-adjusted tradeoffs
• Inflation Calculator — determine whether your fixed DCA contribution maintains its real value over time, or whether you need to increase contributions to offset purchasing power erosion