Full transparency: here are all the mathematical formulas used by the simulator to project the growth of your ETF portfolio — from compound interest to each country's taxation.
The heart of the simulator. We don't apply the return once a year, but every month, to match a regular investment (DCA). We first convert the annual rate into an equivalent monthly rate:
Then, each month, the contribution is added at the start of the month, then the whole grows:
The TER (Total Expense Ratio) is the annual fee charged by the ETF (typically 0.12–0.20%/yr for an MSCI World). Rather than deducting it bluntly once a year, we build it directly into the net rate, which is more accurate:
Over 30 years, a TER of 0.20% instead of 0.60% can amount to tens of thousands of euros of difference — hence the importance of choosing low-fee ETFs.
Some traditional banks charge annual custody fees (0.15–0.30%/yr), whereas neo-brokers (Trade Republic, DEGIRO…) are often at 0%. They are treated like the TER, reducing the net rate:
Earning 7% when inflation is 2% is not earning 7% of purchasing power. So the simulator also shows the real value of your capital, adjusted for inflation:
The “estimated real net return” shown at the top of the simulator combines everything:
This is what sets this simulator apart from a basic calculator. Each country has its own rules.
TOB (stock exchange tax) levied on each purchase and sale, with a rate that depends on the ETF type:
| ETF type | TOB rate |
|---|---|
| Accumulating registered in Belgium | 1,32% |
| Accumulating not registered | 0,12% |
| Distributing | 0,12% |
| ETC (commodities) | 0,35% |
Since 2026, a 10% tax applies to net capital gains > €10,000/yr (annual allowance). Below that, gains are exempt. Key point: a distributing ETF pays out dividends subject to the 30% withholding tax, whereas an accumulating ETF reinvests them automatically and avoids this withholding — which is why accumulating is often preferred in Belgium.
One of the most favourable regimes: capital gains on private wealth are exempt (0%). Only a federal stamp duty of 0.15% applies to purchases of foreign ETFs (0.075% for Swiss ones). Dividends remain taxed as income.
Capital gains are taxed at a 50% inclusion rate: only half the gain is added to taxable income (≈ 27% effective in Ontario, high brackets). The TFSA (tax-exempt, cap ~$7,000/yr) and RRSP (tax deferral) change the game.
The simulator handles a phase of withdrawals (income, retirement, FIRE). The famous 4% rule (Trinity study, 1998) estimates you can withdraw 4% of your capital the first year, then adjusted for inflation, without depleting your portfolio over 30 years:
Each withdrawal triggers the corresponding tax calculation (realised gain), depending on the country.
No. It's a linear historical average (MSCI World ~10%/yr over 30 years). In reality, volatility and the order of crashes (sequence risk) make the result vary, especially during the withdrawal phase.
During the accumulation phase, the accumulating ETF is often more tax-efficient (no withholding on dividends, automatic reinvestment). The distributing ETF may suit the income phase. The simulator applies the right taxation based on your choice.
No. All calculations are done locally in your browser. Nothing is sent to a server.