Dollar-Cost Averaging Calculator Formula

Understand the math behind the dollar-cost averaging calculator. Each variable explained with a worked example.

Use the Dollar-Cost Averaging Calculator

Formulas Used

Future Value

future_value = monthly_return > 0 ? monthly_investment * (pow(1 + monthly_return, total_months) - 1) / monthly_return : total_invested

Total Invested

amount_invested = total_invested

Investment Gains

investment_gains = (monthly_return > 0 ? monthly_investment * (pow(1 + monthly_return, total_months) - 1) / monthly_return : total_invested) - total_invested

Total Gain

gain_percentage = total_invested > 0 ? ((monthly_return > 0 ? monthly_investment * (pow(1 + monthly_return, total_months) - 1) / monthly_return : total_invested) - total_invested) / total_invested * 100 : 0

Variables

VariableDescriptionDefault
monthly_investmentMonthly Investment(USD)500
yearsInvestment Period(years)10
annual_returnExpected Annual Return(%)8
monthly_returnDerived value= annual_return / 12 / 100calculated
total_monthsDerived value= years * 12calculated
total_investedDerived value= monthly_investment * total_monthscalculated

How It Works

Dollar-Cost Averaging (DCA)

DCA involves investing a fixed amount at regular intervals, regardless of market conditions.

How DCA Works

  • When prices are high, your fixed amount buys fewer shares
  • When prices are low, your fixed amount buys more shares
  • Over time, your average cost per share smooths out

    • Future Value Formula

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

    Where PMT is the monthly investment, r is the monthly return, and n is total months.

    DCA vs Lump Sum

    Historically, lump-sum investing outperforms DCA about 2/3 of the time. However, DCA reduces the emotional risk of investing at a peak and is the natural approach for income earners.

    Worked Example

    $500/month for 10 years at 8% annual return.

    monthly_investment = 500years = 10annual_return = 8
    1. 01Monthly return = 8% / 12 = 0.667%
    2. 02Total months = 120
    3. 03Total invested = $500 x 120 = $60,000
    4. 04Future value = $500 x [(1.00667)^120 - 1] / 0.00667 = $91,473
    5. 05Investment gains = $91,473 - $60,000 = $31,473

    Frequently Asked Questions

    Is dollar-cost averaging a good strategy?

    DCA is an excellent strategy for regular investors who receive income over time. It removes the need to time the market and enforces consistent saving discipline. It is the natural way most people invest through 401(k) and IRA contributions.

    Should I lump sum invest or DCA?

    If you have a lump sum available, investing it all at once historically produces higher returns about 66% of the time. If you are risk-averse or worried about timing, DCA provides smoother entry and peace of mind.

    How often should I invest with DCA?

    Monthly is most common and practical. More frequent investing (weekly or biweekly) has minimal mathematical advantage. The key is consistency, not frequency.

    Learn More

    Guide

    Understanding Stock Market Returns

    Learn about historical stock market returns, how to measure investment performance, the difference between nominal and real returns, and what to realistically expect from equity investing.

    Ready to run the numbers?

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