Compound Interest Calculator
See how a lump sum grows with compound interest: enter capital, rate and term to get the final amount, interest earned and a year-by-year chart and table.
Final capital
€16,288.95
Total interest
€6,288.95
Of which compound interest
€1,288.95
Without compounding (simple interest) you would have only €15,000.00. The compound interest effect adds €1,288.95. Assumption: interest credited annually.
Capital growth
| Year | Cum. interest | Of which compound interest | Without compounding | With compounding |
|---|---|---|---|---|
| 1 | €500.00 | €0.00 | €10,500.00 | €10,500.00 |
| 2 | €1,025.00 | €25.00 | €11,000.00 | €11,025.00 |
| 3 | €1,576.25 | €76.25 | €11,500.00 | €11,576.25 |
| 4 | €2,155.06 | €155.06 | €12,000.00 | €12,155.06 |
| 5 | €2,762.82 | €262.82 | €12,500.00 | €12,762.82 |
| 6 | €3,400.96 | €400.96 | €13,000.00 | €13,400.96 |
| 7 | €4,071.00 | €571.00 | €13,500.00 | €14,071.00 |
| 8 | €4,774.55 | €774.55 | €14,000.00 | €14,774.55 |
| 9 | €5,513.28 | €1,013.28 | €14,500.00 | €15,513.28 |
| 10 | €6,288.95 | €1,288.95 | €15,000.00 | €16,288.95 |
Note: These calculations are for informational purposes only and do not replace professional tax or financial advice. All information without guarantee.
FAQ
Frequently Asked Questions
Why is compound interest so powerful?
Compound interest accelerates wealth growth because you earn interest on previously earned interest. Over decades, even small regular investments can grow to significant amounts thanks to this exponential effect.
How does the Rule of 72 work?
Divide 72 by the annual interest rate to estimate how many years it takes to double your money. For example, at 6% interest, your capital doubles in approximately 12 years.
Are my entered amounts stored anywhere?
No. All calculations happen exclusively in your browser. Your inputs are never sent to our server or stored. You can safely enter sensitive financial data.
Guide
What is the Compound Interest Calculator?
The compound interest calculator demonstrates the effect of compound interest over long periods. It shows how reinvested interest accelerates capital growth exponentially.
How does the Compound Interest Calculator work?
Enter starting capital, interest rate and duration. The calculator compares simple interest (linear) with compound interest (exponential, interest credited annually) and shows the difference. A chart illustrates the growing gap over the years. For regular contributions use the interest calculator or the savings calculator.
Key Data and Facts
Formula: final capital = initial capital * (1 + rate)^years. Rule of 72: doubling time in years is approximately 72 / interest rate in percent.
Step-by-Step Guide
How to calculate compound interest step by step: 1. Enter the initial capital: the amount you want to invest today. 2. Set the interest rate: the annual return in percent (e.g. fixed deposit about 2.3–2.7 % according to ECB interest rate statistics 08/2026, ETF historically 7 %). 3. Choose the term: the longer it is, the stronger the compound interest effect. 4. Calculation: final capital = initial capital x (1 + interest rate/100)^years (interest credited once a year). 5. Compare the result: simple interest (linear) vs. compound interest (exponential) – the calculator shows the interest on interest separately. Example: 10,000 EUR initial capital, 5 % interest rate, 20 years, no savings rate. Final capital with compound interest: 10,000 x 1.05^20 = 26,533 EUR. Final capital with simple interest: 10,000 + (10,000 x 0.05 x 20) = 20,000 EUR. Difference: 6,533 EUR – solely due to the compound interest effect. Rule of 72: doubling time = 72 / 5 = about 14.4 years.
Calculation Example
10,000 EUR starting capital, 5% interest, 20 years. With compound interest: 26,533 EUR. Without compound interest (simple interest): 20,000 EUR. Additional yield from compounding: 6,533 EUR. Doubling time (rule of 72): approx. 14.4 years.
Sources
Official sources
Calculations are based on applicable German laws and official data:
- Deutsche Bundesbank
- Bundesanstalt für Finanzdienstleistungsaufsicht (BaFin)
- Statistisches Bundesamt (Destatis)
Full methodology at Methodology.
Reviewed by Konstantin Iakovlev · Last updated:
Finance
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