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Compound Interest Calculator
Calculate the growth of your investment through compound interest over the years.
✅ Free
📅 Updated 22.9.2026
Taxation 2026
About this calculator
What is the Compound Interest Calculator – investment growth?
The compound interest calculator shows how an investment grows when returns generate their own returns year after year. Einstein called it the “eighth wonder of the world” – and for good reason.
The calculator is free, works in your browser without registration, and provides results instantly. All calculations are based on standard formulas; always check the rules that apply where you live.
Formula and calculation principle
Final amount = Initial capital × (1 + r)^n + Monthly investment × ((1+r)^n − 1) / r
The calculator performs the calculation automatically as soon as you enter values into the fields. Results are rounded to two decimal places.
Practical example
Initial investment $5,000, monthly $150, return 7%/year, 30 years → final amount approximately $186,000. Invested $59,000, interest generated $127,000.
You can adjust the calculator’s values according to your situation and get an instantly updated result. Try different scenarios to compare options.
Who is the calculator suitable for?
The calculator is designed for individuals, entrepreneurs, and professionals who need quick and reliable calculations. All calculators are completely free and do not require registration or personal information.
Students and schoolchildren can also benefit from the calculator for learning purposes – the calculator shows not only the result but also the calculation principle, which helps understand the mathematics behind it.
Tips and considerations
- Invest automatically every month – dollar-cost averaging (DCA) smooths out price fluctuations.
- Do not interrupt investing during market turmoil – historically, rises have followed declines.
- Reduce costs: a 1% difference in fees can mean tens of thousands of euros over a 30-year horizon.
Frequently Asked Questions
Compound interest means that you earn returns on previous periods' returns as well – not just on the initial capital. This accelerates the growth of the investment exponentially.
7 % annual return will double your investment in about 10 years (72 rule). Over 30 years, 10,000 $ will grow to over 76,000 $ without additional investments.
The more often interest is added to the principal, the greater the final result. Monthly interest calculation yields more than annual. Most funds use daily calculation.
Over the long term, the stock market has historically produced 7–10 % per year before inflation. The inflation-adjusted real return is about 5–7 %. Past returns do not guarantee future results.
Regular additional investments steadily grow capital. For example, by investing 100 $/month at a 7 % return for 30 years, you will accumulate over 113,000 $.
Inflation erodes the real value of investments. If the return is 7 % and inflation is 3 %, the real return is about 4 %. Our calculator shows both nominal and real values separately.