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Compound Interest Calculator

Calculate how your wealth grows through compound interest over the years.


Result

Final Capital € 0
Interest Earned € 0
Total Deposits € 0
Effective Rate 0%
Doubling Time 0 Jahre
Year-by-Year Development
Year Deposits Interest (Year) Interest (Total) Capital

What is Compound Interest?

Compound interest is a powerful effect in long-term wealth building. It calculates interest not only on the original capital but also on previously earned interest. Albert Einstein reportedly called compound interest the "eighth wonder of the world."

The Compound Interest Formula

Final Capital = Initial Capital × (1 + Interest Rate/n)^(n×Years)

Where n is the number of compounding periods per year (e.g., 12 for monthly compounding).

Example of Compound Interest Effect

For an investment of €10,000 at 5% interest:

  • After 10 years: €16,289 (without compounding it would only be €15,000)
  • After 20 years: €26,533 (without compounding: €20,000)
  • After 30 years: €43,219 (without compounding: €25,000)

The Rule of 72

A simple rule of thumb for calculating doubling time: Divide 72 by the interest rate. At 6% interest, your capital doubles approximately every 12 years (72 ÷ 6 = 12).

Tips for Long-term Investing

  • Start early: The longer the investment horizon, the stronger the compound effect
  • Save regularly: A monthly savings plan amplifies the effect
  • Reinvest returns: Don't withdraw earnings, let them work for you
  • Minimize costs: High fees significantly reduce the compound effect

Frequently Asked Questions

With simple interest, interest is calculated only on the original capital. With compound interest, interest is calculated on the capital plus all previously accrued interest. This causes wealth to grow exponentially instead of linearly.

The more frequent the compounding, the higher the effective interest rate. Monthly compounding is therefore better than annual. The difference is more pronounced at higher interest rates.

Inflation reduces the real return. For example, if you receive 5% interest and inflation is 2%, your real return is only about 3%. For meaningful calculations, you should account for inflation.