Compound interest calculator
Simulate how savings or an investment grow with monthly compounding and regular contributions.
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How it is calculated
Each month: balance = balance × (1 + r / 12 / 100) + contribution
With compound interest, interest earns interest, so growth accelerates over time. The rule of 72 gives a quick estimate: money doubles in about 72 / rate years.
The simulation ignores taxes, fees and inflation, and real investment returns vary from year to year.
Frequently asked questions
What is the difference between simple and compound interest?
Simple interest is always calculated on the original amount; compound interest on the amount plus accumulated interest.
How long does it take to double money at 7 %?
By the rule of 72, about 10.3 years.
Does it include taxes?
No. Investment gains are taxed according to the rules of each country.