The calculator works in a few steps — first you enter how much and how long you want to invest, then you build a portfolio from the available instruments, and finally you click Calculate and read the results. Below you will find a detailed description of every field.
1
Starting amount
The amount of money you put in at the very start — one time only. It can be any amount. If you are starting from zero, enter 0.
2
Investment horizon
How many years you plan to invest for. The longer the time, the bigger the effect of compound interest. Typical values are 10, 20 or 30 years.
3
Regular contributions
The amount you add regularly — monthly, quarterly or yearly. Choose the tab with the frequency you want and enter the amount. If you do not plan to add money regularly, choose "No contributions".
You do not need a large starting amount. The calculator shows that regular small contributions over 20 years often give a better result than one big lump sum with no top-ups.
02Return adjustment
Adjust the expected result to your assumptions
The return adjustment slider lets you check what happens if the market performs worse or better than the historical average. It does not change your portfolio — it just adds or subtracts a percentage from every instrument.
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–1% to –5% (pessimistic)
Simulates weaker returns — useful for checking the worst realistic scenario.
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0% (base)
Default setting — uses the historical average return for each instrument in your portfolio.
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+1% to +5% (optimistic)
Simulates better returns — shows the potential in a favourable market.
Tip: Set the slider to –2% and check the result — this is a good test of whether your investment plan still makes sense even with slightly weaker returns.
03Options and taxes
Turn on the factors that matter for your situation
In the Options & Taxes section you turn on or off extra factors that affect the result. Each one is optional — you can turn them on one by one and watch how the final result changes.
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Capital gains tax
Turn this on to make the calculator subtract tax from your profit at the end. Enter the rate for your country or click one of the presets (USA, Germany, France, UK, Canada, Italy, Spain).
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Inflation
Turn this on to see the real purchasing power of your portfolio — what your money will actually be worth in today's prices. The default rate is 2.5%, but you can change it.
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Dividend reinvestment (DRIP)
When on, dividends paid by your ETF are automatically reinvested — buying new units instead of paying out cash. Over the long term this significantly increases the result.
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Fund fees (TER)
TER (Total Expense Ratio) is the annual management fee for your ETF — usually 0.07%–0.5%. Turn it on and enter your ETF's TER to see the real impact of fees on your final result.
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Compare with bank deposit
Adds a bank deposit line (3.5% per year) to the chart so you can compare whether and by how much your ETF portfolio beats a safe deposit.
Start by turning on capital gains tax and inflation — these two are the most important factors for seeing the real result of your investment. You can add the others gradually.
04Portfolio builder
Choose instruments and set your allocation
The portfolio builder is the heart of the calculator — here you decide what to invest in and in what proportions. You can add from 1 to several instruments.
1
Click "Add instrument"
A window opens with a list of available instruments: stock ETFs, bonds, precious metals, real estate (REITs), commodities, cryptocurrencies and individual company stocks. You can search the list by typing a name.
2
Select your instruments
Click on an instrument to add it to your portfolio (a ✓ mark will appear). You can add several at once. Click again to remove it.
3
Set the percentage allocation
Next to each instrument enter what percentage of the portfolio it should take up. All percentages must add up to exactly 100% — the bar at the top shows the current total and turns green when you reach 100%.
4
Użyj „Wyrównaj" dla prostszego startu
Use "Balance
5
Or load a ready-made example
Przycisk „Przykład pasywny" wczytuje portfel oparty na popularnej strategii pasywnej — dobry punkt startowy do własnych modyfikacji.
The "Passive example
Tip: A single global ETF (e.g. MSCI World) set to 100% is a completely valid portfolio for a beginner. You do not need to make it complicated.
05How to read the results
What does each results section mean?
When your portfolio is ready and the total is 100%, click the blue "Calculate portfolio results" button. The results will appear below — split into several sections.
📊 Summary cards
Four numbers at the very top of the results — the most important summary:
Final value
247,832
How much your portfolio will be worth at the end, after tax.
Total deposited
130,000
The total of all your contributions — starting amount and regular top-ups.
Net profit
+117,832
How much you earned above your contributions, after tax.
Portfolio return
7.4% / year
Weighted annual return of the whole portfolio (average across instruments).
📈 Capital growth chart
The amber line is your ETF portfolio, the blue line is a bank deposit (if you turned it on). The gap between them shows your portfolio's advantage over the deposit — the wider the better. Hover over any year to see the exact values.
🥧 Portfolio composition
The pie chart shows the percentage share of each instrument. A quick check that your portfolio looks the way you intended — and that it is not dominated by a single asset.
📋 Scenario comparison
Three cards show the result under different assumptions: pessimistic (–3%), base and optimistic (+3%). They give a feel for the range of possible outcomes — a realistic minimum and maximum.
⚡ Portfolio risk rating
The risk rating on a scale of 1–5 is calculated as the weighted average volatility of your instruments. Low risk (1–2) means bonds and deposits. High risk (4–5) means cryptocurrencies and individual stocks. A mixed portfolio usually lands around 3.
🎲 Monte Carlo simulation
The calculator runs 1,000 random investment paths, simulating market unpredictability. Instead of one line you see a whole band of possible outcomes:
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Wide golden band (P10–P90)
80% of all simulations fall within this range. This is your realistic range of outcomes.
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Narrower inner band (P25–P75)
Half of the simulations fall in this narrower range — the most likely outcomes.
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Median line (P50)
Exactly half of the paths ended higher, half lower. The single most realistic number.
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Dashed line (deterministic)
The classic result without randomness — the same as the numbers in the summary cards above.
The wider the Monte Carlo band, the greater the uncertainty — which is normal for high-risk portfolios (e.g. lots of crypto). A narrow band means a more predictable result (e.g. a bond-heavy portfolio).
📉 Historical crashes
This section shows how your specific portfolio would have behaved during the 7 biggest market crashes in history — the 1929 crash, the dot-com crash of 2000, the 2008 financial crisis and others. For each crash you see: the percentage drop in your portfolio value, the estimated loss in money, and the time needed to recover. Green values mean that instrument went up during the crash (e.g. government bonds, gold).
Every crash shown was historically recovered from. This section is not meant to scare you — it is meant to show that even big drops are a normal part of investing and that patience pays off.
📅 Yearly breakdown
The table shows year by year: total contributions, portfolio value, gross profit, tax charged, net profit and ROI. If you turned on inflation, a column showing the real value of your portfolio in today's purchasing power also appears.