Investment Calculator: Project Your Portfolio for Retirement in SEA
Free compound interest calculator. See how your starting amount, monthly contributions, return rate, and investment length shape your end balance.
- • Contributions are made monthly, at the end of each month.
- • Return is compounded monthly at (annual rate / 12).
- • Return rate is a constant nominal rate — no year-to-year variation modelled.
- • Ignores taxes, fees, and inflation. For real (inflation-adjusted) growth, subtract ~2–3% from your return rate.
How this calculator works
This is a compound interest calculator with monthly contributions — the same math that sits behind every retirement projection tool on the internet. Give it your starting amount, how much you'll add each month, how long you'll invest, and what return you expect. It returns your projected end balance, broken down into three parts: the starting amount you put in, the total of your ongoing contributions, and the interest earned on top.
The formula is:
End Balance = P × (1 + r)ⁿ + PMT × ((1 + r)ⁿ − 1) / r
Where P is your starting amount, r is the monthly return rate (annual rate divided by 12), n is the number of months (years × 12), and PMT is your monthly contribution. When you enter 0% return, the formula collapses to simple addition — starting amount plus all your contributions with no growth on top.
Compounding is what does the heavy lifting
The counterintuitive part of long-term investing is not how much you contribute — it is how much time you give the interest to compound on top of previous interest. Fifteen years of $500/month at 7% builds to about $158,000 in contributions turning into a $189,000 end balance. Thirty years at the same $500/month and 7% builds to $180,000 in contributions turning into a $612,000 end balance. Double the time, triple the balance. That gap is compounding.
The practical implication for anyone planning retirement is simple: the single most valuable variable in this calculator is the "Investment Length" field, and the single worst thing you can do is delay starting by a decade to "figure things out." A 30-year-old contributing $300/month ends up with a larger balance at 65 than a 40-year-old contributing $600/month, at the same return rate.
What return rate to actually use
The default here is 7% because it is a defensible planning number for a globally diversified equity portfolio: it undershoots the S&P 500's historical ~10% nominal average and roughly matches its ~7% real (inflation-adjusted) average. If your portfolio holds bonds, use a lower number — a 60/40 stock/bond mix has historically returned closer to 5–6% nominal. If you are comfortable with volatility and holding 100% equities for a long horizon, 8–9% is not unreasonable, but expect drawdowns of 40%+ in bad years.
The trap in this field is that small changes matter enormously over long horizons. The difference between 6% and 8% over 30 years on a $500/month contribution is roughly $250,000. Do not tune this number to make the End Balance look attractive — tune it to what your actual portfolio is likely to earn.
Who this tool is for
Anyone planning retirement in Southeast Asia — or anywhere else — who needs a fast answer to "if I keep saving X per month at Y return, how much will I have when I want to move?" It is a projection, not a plan. It ignores taxes, fees, inflation, and currency risk. All four of those matter, particularly the last two if your expenses will be in Thai baht or Vietnamese dong while your portfolio is in USD.
Use this to build intuition and stress-test scenarios. Use a proper planner or Monte Carlo tool for the plan itself.
Frequently asked questions
›What return rate should I use?
For a diversified global equity portfolio, 7% nominal is a conservative long-term assumption. The S&P 500 has averaged closer to 10% nominal / 7% real over the past century. For a 60/40 stock/bond mix, 5–6% nominal is a reasonable planning number.
›Does this account for inflation?
No — the End Balance is stated in nominal (today's) dollars using the return rate you enter. If you want a real return figure, subtract expected inflation (roughly 2–3% for USD) from your return rate before running the calculation.
›Does this account for taxes?
No. In taxable accounts, dividends and realized gains reduce the effective return by roughly 0.5–1.5 percentage points depending on your bracket. Tax-advantaged accounts (Roth IRA, 401k, HSA) are unaffected.
›Should I invest a lump sum or spread it out?
Historically, lump-sum investing has outperformed dollar-cost averaging about two-thirds of the time — the market goes up more often than it goes down. But DCA reduces regret risk if you invest right before a drawdown. This calculator can model either: set a large Starting Amount and $0 monthly for lump-sum, or $0 starting and a large monthly for pure DCA.
›How does this apply to retirement in SEA?
Your portfolio stays USD-denominated but your SEA expenses are in local currency. A 15–20% USD strengthening or weakening changes your real spending power. That's a risk this calculator does not model — treat the End Balance as the upper bound of what you can plan on.
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