Power of Compounding: ETF Savings Plan Calculator & Compound Interest Calculator

Our compound interest calculator helps you visualize the powerful effect of compound interest of a savings plan in Germany.
Last updated on February 18, 2026

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Compounding is the effect of interest on interest. Einstein called compounding the Eighth World Wonder because the effect is so powerful. The longer assets are invested at a high yield, for example in an ETF savings plan, the steeper the impact on the value.

Research shows that people who use the Rule of 72 make the best predictions. This rule says that with a return of 7,2 %, your money doubles every 10 years. So in:

  • 10 years: 2x your money

  • 20 years: 4x your money

  • 30 years: 8x your money

  • 40 years: 16x your money

Pensionfriend aims for a return of over 7,2 % after cost and tax, about 2% more than investing in a global ETF index, the MSCI. Make a free appointment here

Investfriend aims for even higher returns, but it does require a higher income to afford a new investment property. You can check the details here.

Dr. Chris Mulder

Dr. Chris Mulder

Dr. Chris is a former Senior Economist and Manager at the IMF and The World Bank. He is a Hypofriend Co-founder.

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