DCA Calculator: Recurring Contributions, Returns & Limits
TL;DR
- The FundamentalRadar DCA calculator reconstructs what would have happened if you had made equal monthly contributions on the historical price path of an asset or index; it does not model an assumed future return.
- Enter the asset, start and end dates, and a monthly contribution. Each contribution is applied on the first trading session of its month.
- Read net value, net return, IRR, costs, and benchmark comparisons as a historical reconstruction, not a forecast.
- Compare scenarios by changing one premise at a time and checking the period, currency, inflation, and available history.
Dollar-cost averaging (DCA) is the practice of investing money in equal portions, at regular intervals, regardless of the ups and downs in the market. This is the definition used by Investor.gov. The approach brings discipline, but it does not eliminate losses or guarantee a favorable average price.
FundamentalRadar turns this idea into a historical simulation. Rather than projecting compound interest at a rate you choose, the tool reconstructs what would have happened with monthly contributions on the asset and in the interval you specify. This lets you study a concrete period without confusing past results with future predictions.
What the DCA calculator actually computes
On the simulator page, four inputs define the scenario:
| Input | Effect on the calculation | Verification |
|---|---|---|
| Asset or index | Selects the historical series and the currency | Check the ticker, market, and displayed name |
| Start date | Sets the month of the first contribution | Check that the asset had history back that far |
| End date | Limits the last close considered | Compare periods with the same end date |
| Monthly contribution | Sets the recurring nominal flow | Inflation does not adjust the contribution |
Each contribution is applied on the first trading session available in its month. The calculation uses the adjusted close reported by the asset itself, separates contributed capital, result, and costs. If the asset lacks data back to the requested start date, the tool shortens the window and warns; in that case, the total invested is also lower.
This approach differs from a compound-interest calculator. The Investor.gov compound interest calculator starts from an estimated rate. FundamentalRadar starts from observed prices. The two answer different questions: one explores a mathematical hypothesis; the other reconstructs a specific historical path.
Configurable taxes and costs
The withdrawal assumptions panel lets you enter brokerage per order, annual custody, and, when the market supports it, trading fees and an estimated tax on gains. These are user assumptions, not individual tax accounting.
| Field | How to interpret it | Source |
|---|---|---|
| Estimated tax | Reduction applied to gains based on the configuration available | Investor.gov — Fees and expenses |
| Brokerage | Nominal cost assigned to each monthly order | FINRA — Dollar-cost averaging |
| Trading fees | Estimated percentage when the selected market offers this field | Investor.gov — Fees and expenses |
| Annual custody | Percentage you enter to estimate the maintenance cost | Investor.gov — Fees and expenses |
An empty or zeroed field means a zero-cost assumption, not that every broker or investment is free. To compare two alternatives, fix the asset and dates and change only the costs.
How to read the results
The first card shows the estimated net value, alongside the gross value and the sum of costs and tax. The figure is nominal; when the result includes an inflation reference, the screen also shows the corresponding real return.
The net return measures the outcome after the configured deductions. Beside it, the gross comparison against the benchmark. Because the bases can differ, read the comparison label before concluding that one alternative beat another.
The annualized IRR accounts for the timing of each contribution. It is more appropriate to a monthly flow than dividing the gain by the number of years. In short or degenerate windows, the tool may omit annualization rather than display an unstable rate.
For the low-risk reference, the panel applies the same contribution schedule to the available risk-free leg. That figure is therefore not simply the accumulated rate over the period: it respects the gradual arrival of money.
The wealth-over-time chart shows the trajectory. The composition splits contributed capital, gain or loss, and costs. The monthly table lets you check date, contribution, price used, and the evolution of positions. Use this breakdown to see why two seemingly identical scenarios ended differently.
The benchmark is context, not a goal
A benchmark provides context, but it does not turn past performance into an expectation. The asset, the comparison index, and the risk-free reference can have different risks, currencies, tax treatment, and return bases.
FINRA notes that investing gradually can reduce the risk of putting all money in at an unfavorable moment, but it can also sacrifice return when prices rise and money stays out of the market (FINRA). That is a comparison of entry methods, not a projection for the next period.
When studying stocks, pair the simulation with the financial indicators guide. To understand the environment of the period, see the Brazilian market dashboard. If daily movement caught your attention, also read how to interpret B3 highs and lows.
A reproducible comparison procedure
- Choose the asset and confirm its market, currency, and available history.
- Set dates that include different market phases, not just a favorable stretch.
- Enter the nominal contribution you want to study.
- Fill in costs consistent with the scenario being compared.
- Run and record the inputs before looking at the result.
- Read the net value, contributed capital, IRR, benchmark, and cost breakdown.
- Change one premise at a time and run again.
Changing the asset, period, contribution, and costs together makes it impossible to know which variable explained the difference. A useful test keeps the flow and dates fixed to compare assets; another keeps the asset fixed to compare windows.
Simulation limits
The result depends entirely on the historical window chosen. A window can start before a rally, after a decline, or during a crisis. Picking dates after knowing the result introduces hindsight bias.
The contribution is nominal and fixed. The tool does not model salary growth, income interruption, mid-window withdrawals, or a portfolio rebalanced across several assets. It also does not replace the investor's tax accounting.
Adjusted closes make comparisons easier over time, but they do not make series from different providers automatically equivalent. Check the basis warnings on screen, especially when comparing markets.
Lastly, DCA does not protect against a permanent decline in the asset. Investor.gov defines the regularity of the method, not a profit guarantee (Investor.gov). Investment quality still depends on the asset, price, horizon, and the investor's financial capacity.
Common errors and fixes
| Error | Cause | Fix | Source |
|---|---|---|---|
| Treating the result as a future projection | Confusing historical reconstruction with prediction | Always describe the asset, dates, and assumptions used | Investor.gov — DCA |
| Comparing different windows | The period explains part of the difference | Fix the dates before changing the asset | FINRA — DCA |
| Ignoring the shortened-history warning | The asset started trading after the requested date | Use the effective date shown and check the total invested | Investor.gov — Calculators |
| Zeroing costs without noticing | Empty or zero fields become scenario assumptions | Record brokerage, custody, and other applicable costs | Investor.gov — Fees |
| Comparing only the final balance | Contributions and costs may differ | Also compare capital, net return, IRR, and composition | Investor.gov — Savings goal |
FAQ
Does the DCA calculator guarantee the return shown?
No. It reconstructs a result from historical data and the assumptions you enter. The future may follow a different path.
Do I need to enter an expected return?
No. The calculator uses the historical series of the chosen asset. The annualized rate shown is the result of the simulation, not an input.
When are contributions made?
On the first trading session available in each month within the selected window.
Does the final value already subtract costs?
The panel separates gross value, net value, and estimates of costs and tax according to the fields available and filled in.
Can I simulate weekly or growing contributions?
The main flow is monthly and nominally fixed. To study another flow, do not assume the screen reproduces it; treat it as a separate analysis.
How do I compare two assets?
Use the same dates, the same contribution, and the same cost assumptions. Then compare net return, IRR, benchmark, and composition, not just the final balance.
Why can the start date change?
If there is not enough history, the simulation starts on the first available date and reports that the window was shortened.