Compound Interest Calculator

Q: How is compound interest calculated here?

The calculator compounds monthly using a net monthly rate derived from the net annual return. Each month the portfolio grows by the monthly rate, then the monthly contribution is added.

Q: Why do fees matter so much over decades?

Fees reduce net return every year. Over long horizons, the fee drag can compound into a large difference in final value.

Compound Interest Calculator (2026) — Monthly Contributions & Fees | AlphaTechFinance

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Compound Interest Calculator (ATF)

Calculate compounding with an initial investment and monthly contributions. Add fees (TER) and inflation to see the difference between nominal and real outcomes.

Educational tool only. Not financial, tax, or legal advice.

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Initial investment (€)

Monthly contribution (€)

Time horizon (years)

Expected annual return (%)

Advanced options (fees & inflation)

Annual fee / TER (%)

Inflation (%)

Fees are modeled as net-return drag. Inflation estimates purchasing power in today’s euros.

Final value (nominal)

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Final value (real, inflation-adjusted)

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Total contributions

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Total interest / growth

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Net annual return (gross − fee)

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Approx. CAGR (net)

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Growth chart

Yearly values with monthly compounding

FAQ

How is compound interest calculated here?

We compound monthly using a net monthly rate derived from the net annual return. Each month: portfolio grows by the monthly rate, then the monthly contribution is added.

Why do fees matter so much over decades?

Fees reduce your net return every year. Over 20–30 years, that small drag can compound into a large difference.

What is the difference between nominal and real value?

Nominal is the raw future value. Real adjusts for inflation to estimate purchasing power in today’s euros.