Compound Interest Calculator
Estimate how your savings or investment grow over time. Free, fast and easy to use.
How it works
With compound interest you also earn interest on interest you have already earned. Enter the starting amount, the annual rate, the number of years and an optional monthly contribution. Taxes, fees and inflation are not included.
Formula
A = P × (1 + r/n)^(n·t)
Worked examples
- Initial investment (€): 5000 · Annual interest rate (%): 5 · Years: 20 · Compounding: Monthly · Monthly contribution (€): 100 → Final balance: €54,666.57
- Initial investment (€): 10000 · Annual interest rate (%): 3 · Years: 5 · Compounding: Yearly · Monthly contribution (€): 0 → Final balance: €11,592.74
Calculations run locally in your browser. Results are for information only — for engineering, electrical or financial decisions, verify the assumptions and applicable standards.
Frequently asked questions
How does compound interest work?
Interest is added to the balance and later interest is calculated on the larger balance. €10,000 at 6 % a year grows to €17,908 in 10 years.
What is the rule of 72?
Divide 72 by the annual interest rate to estimate how many years it takes to double your money – at 6 % about 12 years.