Compound Interest Calculator
See how your money grows with compound interest, compounded annually or monthly, plus optional regular deposits. Includes a year-by-year breakdown. Runs entirely in your browser.
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Legal notice
Current as of: 11.08.2026.
The results reflect the legal and fiscal state as of the date stated above. They are provided for general information and initial guidance only. They are not individual financial, tax or legal advice, and no guarantee is given as to their accuracy, completeness or suitability for your circumstances. In particular, the results are not a substitute for an official or judicial assessment. Please check the information independently and seek qualified advice where appropriate, as you are solely responsible for any decision made in reliance on the result.
Compound Interest Calculator: final capital, interest earned, and deposits
When you invest money, you benefit from the compound interest effect: the interest you earn is reinvested and itself earns interest the following year. With the compound interest calculator you can find out how strongly your capital grows over the years, whether you invest a one-off amount or pay in regularly. You see the final capital, the pure interest earned, and a yearly breakdown over the whole term.
You enter the starting capital, the interest rate, the term, and optionally a regular deposit. The calculator accounts for whether interest is compounded annually or monthly and shows you in a table how your wealth develops year by year. This lets you compare different savings plans and investment ideas directly.
As a guide for your interest rate: high-yield savings accounts and fixed deposits in Germany currently pay roughly 2 to 4 percent a year depending on the provider and term, with longer fixed deposits often slightly above 3.5 percent (September 2026). The default of 3 percent is therefore a realistic example. For planning, use a more conservative rate, because fees, taxes, and inflation reduce the real return.
Note: This calculation is for orientation and is not financial or investment advice. Actual returns depend on interest-rate development, fees, inflation, and taxes. Please inform yourself in your individual case and seek advice for larger decisions.
How the compound interest calculation works
The compound interest calculator uses the classic formula for the compound interest effect. The starting capital is increased each year by the interest, and in the following year the interest is calculated on the new, higher balance. Regular deposits flow in on top and further strengthen the growth.
- Enter the starting capital, for example €10,000.
- Enter the interest rate, for example 3 percent per year.
- Choose the term, for example 20 years.
- Optionally add a monthly or yearly deposit.
- The result shows final capital, interest earned, and the yearly development.
What it can and cannot do
The calculator suits savings plans, fixed deposits, high-yield savings accounts, and long-term wealth building, and makes the compound interest effect tangible. It works with a fixed interest rate and does not account for taxes, fees, or inflation. When those factors are considered, the actual result is usually somewhat lower. For a realistic plan, you can therefore set your interest rate conservatively.
Frequently asked questions
What is the compound interest effect?
With compound interest, the interest you earn itself earns interest the following year. Your capital therefore grows not linearly but ever faster over time. The longer the term, the stronger this effect.
How is the final capital calculated?
The final capital results from the starting capital, which is increased year by year by the interest on the current balance. Regular deposits add to it. The calculator runs this calculation for every year of the term.
What is the difference between annual and monthly compounding?
With monthly compounding, interest is credited twelve times a year and reinvested directly. At the same interest rate, this leads to a marginally higher final amount than pure annual compounding.
Are taxes and fees included?
No. The calculator works with a fixed interest rate and without deductions for taxes, fees, or inflation. For a realistic plan you should factor these in yourself, for example by using a somewhat lower assumed interest rate.
What rates are realistic to use for planning?
High-yield savings accounts and fixed deposits in Germany currently pay roughly 2 to 4 percent a year depending on the provider and term, with longer fixed deposits often slightly above 3.5 percent (September 2026). The default of 3 percent is a realistic example. For planning, use a more conservative rate, because taxes, fees, and inflation reduce the real return.
What happens when I set the savings rhythm to none?
Then no regular deposit is counted, even if a value is still in the field. The field is greyed out. Only the starting capital and its interest apply.
Who is the compound interest calculator for?
For anyone who wants to understand how their money grows over time: savers planning a savings plan, investors comparing different rates, and everyone who wants to grasp the difference between simple interest and compound interest.