Dollar-Cost Averaging Calculator (VND)
Dollar-cost averaging (DCA) means investing a fixed amount on a fixed schedule — typically every month — into the same asset (stocks, fund certificates, ETFs), regardless of price. When prices fall, your fixed contribution buys more units; when prices rise, it buys fewer. Over time your average purchase price is smoothed out, and you never have to guess the market's top or bottom. That is why DCA is the default strategy for most busy individual investors: it converts an emotional timing decision into a boring, automatic habit.
If you live and work in Vietnam, the practical version is an automatic monthly transfer in Vietnamese dong into a brokerage or fund account on payday. The arithmetic that makes it powerful is the combination of contribution discipline and compounding. Under an illustrative 10%/year return, investing 5.000.000 VND every month for 15 years means you pay in 900.000.000 VND, but the portfolio could reach roughly 2.008.106.091 VND — with about 55% of that ending value coming from growth rather than your own contributions.
The calculator above lets you enter your monthly amount, an assumed annual return and a horizon, then simulates the portfolio year by year. One caveat governs everything on this page: the 10%/year figure is an illustrative assumption, not a promise or a forecast. Equities and funds can and do lose value; past performance does not guarantee future results. Treat the output as a scenario to build intuition, not a number you are guaranteed to hit.
How the calculator computes a DCA plan
The future-value-of-contributions model
DCA is, mathematically, a stream of equal monthly contributions, so its future value is an annuity:
FV = PMT × ((1 + r_m)^m − 1) / r_m × (1 + r_m)
| Symbol | Meaning |
|---|---|
| FV | Portfolio value at the end of the horizon |
| PMT | Fixed monthly contribution |
| r_m | Effective monthly rate = (1 + r)^(1/12) − 1 |
| r | Assumed annual return as a decimal (10% = 0.1) |
| m | Total months = years × 12 |
The tool treats the annual return you type as an effective annual rate and converts it to a monthly rate via (1 + r)^(1/12) − 1, so the portfolio grows by exactly (1 + r) each year. Each contribution lands at the start of the month and immediately starts compounding (annuity-due) — exactly what the simulation does, so every figure in the worked example is reproducible in a spreadsheet.
Why DCA reduces timing risk
- Lump-sum investing requires you to pick a moment. Enter at a local peak and you can sit on a deep paper loss before recovering.
- DCA splits the same money across many scheduled buys. When prices dip, your fixed 5.000.000 VND buys more units and pulls your average cost down. You trade away some expected return — in a long-running bull market, investing everything early tends to win on average — in exchange for lower volatility of outcomes and psychological staying power, which is what keeps most investors from selling at the bottom.
What the model leaves out
The calculator assumes a constant, positive return for the whole horizon. Real markets are volatile — some years are negative — and DCA smooths your entry price, it does not remove the risk of loss. The model also ignores taxes, brokerage fees, fund management fees and inflation. So read the result as a scenario under one fixed assumption, not a prediction. Re-run it with a lower return to stress-test your plan.
Worked example: 5.000.000 VND/month at an illustrative 10%/year
Illustrative assumptions: a constant 10%/year return (for illustration only, not a promise), contributions at the start of every month, no withdrawals, no taxes or fees.
| Milestone | Total contributed | Portfolio value | Growth |
|---|---|---|---|
| Year 5 | 300.000.000 | 385.858.700 | 85.858.700 |
| Year 10 | 600.000.000 | 1.007.287.996 | 407.287.996 |
| Year 15 | 900.000.000 | 2.008.106.091 | 1.108.106.091 |
Three things stand out.
- Growth compounds late. After 5 years you have contributed 300.000.000 VND and earned only 85.858.700 VND; by year 15 your contributions have tripled to 900.000.000 VND, but growth of 1.108.106.091 VND now dwarfs them — the early contributions had far more years to work.
- By year 15, roughly 55% of the portfolio is growth, not money you paid in. The longer you stay invested, the more the market (under this assumption) does the heavy lifting.
- Discipline beats timing. With just 5.000.000 VND a month — an amount many salaried expats can automate — you reach 2.008.106.091 VND in 15 years without ever calling a market top or bottom.
Re-run the calculator with a return you consider realistic for your fund or index, and test a lower figure too. FiMo also has compound-interest and future-value tools if you want to compare DCA against investing a lump sum up front.
Frequently asked questions
What is dollar-cost averaging and how does it work?
Dollar-cost averaging (DCA) is investing a fixed amount on a fixed schedule — usually monthly — into the same asset regardless of price. When prices fall your contribution buys more units; when they rise it buys fewer, so your average cost is smoothed and you never have to time the market. Illustrative example: 5.000.000 VND/month for 15 years at an assumed 10%/year reaches about 2.008.106.091 VND, versus 900.000.000 VND actually contributed.
What is the DCA formula and what do the variables mean?
DCA is a stream of equal monthly contributions, so it uses the future-value-of-an-annuity formula: FV = PMT × ((1 + r_m)^m − 1)/r_m × (1 + r_m), where PMT is the monthly contribution, r_m = (1 + r)^(1/12) − 1 is the effective monthly rate derived from the annual return r, and m = years × 12. Each contribution is added at the start of the month and compounds immediately. Verifiable: 5.000.000 VND/month at 10%/year for 10 years gives 1.007.287.996 VND.
Does DCA actually beat investing a lump sum?
It depends on what you optimise for. DCA reduces timing risk by spreading purchases over many months, so a crash right after you invest does limited damage. But statistically, in a long-running rising market, lump-sum investing tends to deliver a higher expected return because the money is invested sooner. DCA wins on behaviour: it matches a monthly salary, removes the temptation to time the market, and keeps most investors from panic-selling — which is why it is the default for individual investors saving from income.
Is the 10%/year return in the examples a guaranteed result?
No. The 10%/year used throughout this page is an illustrative assumption chosen to keep the math easy to follow — it is neither a promise nor a forecast. Equity and fund returns vary year to year and can be negative, and past performance does not guarantee future results. Enter a rate you consider realistic for your own portfolio, and always stress-test a lower figure to see how sensitive your plan is to weaker markets.
What does the DCA model leave out?
The calculator assumes a constant, positive return every year — real markets are volatile, with negative years, and DCA smooths your entry price without removing the risk of loss. It also ignores taxes, brokerage commissions, fund management fees and inflation, all of which reduce real-world results below the modelled figure. Treat the output as a clean scenario under one fixed assumption, useful for building intuition rather than as a prediction of your actual ending balance.
How much of the final value is growth versus my own money?
The growth share rises with time. In the 5.000.000 VND/month example at an illustrative 10%/year, growth reaches about 55% of the year-15 portfolio of 2.008.106.091 VND, with the remainder being the 900.000.000 VND you contributed. At year 5 the split is far more weighted toward contributions — which is the quantitative case for starting early and staying consistent rather than waiting for a "better" entry point.