What is compound interest?

Compound interest is interest earned on both your initial investment and previously accumulated interest. Unlike simple interest, it creates exponential growth over time.

What's a realistic annual return rate?

Historically, diversified stock market index funds have returned 7-10% per year before inflation over 20+ year periods. Bonds typically return 2-4%. A balanced portfolio might average 5-7%.

How often is interest compounded?

This calculator compounds monthly, which is standard for most investments. The more frequently interest compounds, the faster your money grows.

Does this account for inflation?

No. The results show nominal values. To estimate real (inflation-adjusted) returns, subtract the inflation rate (typically 2-3%) from your expected return rate.

Compound Interest Calculator

See how your money grows exponentially with compound interest and regular monthly contributions.

Growth projection

Initial investment (€)

Monthly contribution (€)

Annual interest rate (%)

Investment period (years)

Growth projection

See how your money grows exponentially with compound interest and regular monthly contributions.

How the compound interest calculator works

This calculator shows how your money grows through the power of compound interest — earning returns on your returns.

Enter your starting amount

How much do you have to invest today? This is your initial lump sum.

Set monthly contributions and rate

Enter how much you'll add each month and the expected annual return. Historical stock market averages are 7-10% before inflation.

See your growth over time

The calculator shows year-by-year growth, separating your contributions from interest earned. Notice how interest accelerates over time — that's compounding.

Track your real compound growth

Use Arfin to track how your actual portfolio compounds over time with real market data, dividends reinvested, and performance benchmarks.

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