ETF calculator: two questions, one calculator for each
“ETF calculator” usually means one of two questions in practice: how does my monthly ETF savings plan grow, or how does a one-time investment grow through compound interest? Planafolio answers both for free.
Pick the right calculator
Which question do you want answered?
Calculate an ETF savings plan
You contribute a fixed amount every month — the savings plan calculator shows how much is contributions and how much is interest earned.
Go to the ETF savings plan calculatorCalculate a lump-sum investment
You invest a one-time amount — the compound interest calculator shows how much it grows over the years.
Go to the compound interest calculatorThe methodology
How the ETF calculator computes its result
No black box — the logic behind it is fully transparent.
Both calculators simulate your capital month by month rather than using a single formula for the whole horizon. Your entered annual return is first converted into a monthly return: (1 + annual return) to the power of (1/12), minus 1. Each month, your existing capital grows by this monthly rate, and then — in the savings plan calculator — your monthly contribution is added. After twelve months of pure compounding with no further contribution, your capital lands exactly at the annual return you entered; compounding is already at work in between, because returns already earned are compounded again the following month.
What the calculator deliberately does not deduct itself: ETF costs (TER) and taxes. So enter your return assumption net of costs — if you're planning with a 7% gross return and your ETF has a TER of 0.20%, try 6.8% instead as a rough approximation. Capital gains tax and the German Vorabpauschale are only factored in by the real portfolio view in Planafolio, because they depend on your personal tax rate and allowance.
What matters
What makes a good ETF calculator
Three things many simple online calculators overlook.
Factor in costs
An ETF's total expense ratio (TER) eats up a noticeable part of the return over decades — a realistic calculator doesn't hide it.
Realistic return assumption
Historical stock market average returns are no promise for the future — the calculator lets you choose the assumption yourself instead of hiding it.
Don't forget taxes
Capital gains tax reduces the actual return — Planafolio accounts for that in the real portfolio view, not just in the model calculator.
Frequently asked questions
ETF calculator questions
An ETF calculator projects how an ETF investment develops over time — either as a recurring savings plan or as a one-time investment, each under an assumed annual return.
If you contribute monthly, use the savings plan calculator. If you're investing an existing amount once, the compound interest calculator is the right choice — you can also combine both.
Both calculators are simplified models with a constant return you choose yourself — real markets fluctuate. They're a general guide, not investment advice or a promised return.
Nothing. The ETF calculator is free to use and requires no registration — like every calculator on this page.
By carrying capital forward month by month instead of just comparing a start and end value: the annual return is converted into a monthly rate, existing capital grows by that rate every month, and returns already earned are automatically compounded again the following month — that's the compounding effect. That's exactly the calculation the ETF calculator on this page runs for you.
Yes. The calculator works independently of the ETF provider — whether iShares, Vanguard, Xtrackers or any other provider makes no difference to the compound-interest math. Differences between providers mainly show up in the TER, which you should subtract from your return assumption as described above.
The calculator models total return — price gains and distributions combined into a single percentage — but doesn't show a separate payout schedule. For the actual dividend dates and amounts of your real portfolio, Planafolio has its own dividend calendar.
Yes, an ETF savings plan is a common building block of private retirement provision. Whether your planned contribution is enough for your desired retirement shows up in the Altersvorsorgedepot calculator: it compares your projected capital at retirement with your actual need and reveals any pension gap.
Yes. The compounding math behind it is independent of the security type — whether ETF, individual stock, or fund, the savings plan and compound interest calculators work identically. Just adjust your return assumption to match the relevant risk.
Keep track of your real ETF portfolio
Planafolio tracks your actual portfolio with XIRR return, tax overview and retirement planning — not just a model.
Get started free