Compound Interest Calculator
Simulate compound interest with initial capital, regular contributions, effective rates and terms.
Result
The percentage is interest divided by total invested; it is not an annualised rate.
Investment growth
Total investedAccumulated value
Monthly table
| Month | Opening balance | Regular contribution | Interest | Closing balance | Total invested | Accumulated interest |
|---|
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Understanding compound interest
Compound interest accrues on principal and previously credited interest. Without contributions: initial capital × (1 + rate per period) raised to the number of periods.
Month-end contributions start earning the following month; contributions at the start earn during that month.
An effective annual rate is converted into an equivalent rate for each compounding interval. Do not directly add or multiply monthly and annual rates.
Compare final value with total invested to identify interest. This mathematical simulation excludes taxes, fees and inflation; it is not investment advice.
Frequently asked questions
How does it differ from simple interest?
Simple interest uses the reference principal. With compound interest, credited interest also earns interest.
What happens with a zero rate?
The result is initial capital plus contributions, with no earnings.
Can I use a negative rate?
Yes, to simulate periodic losses above -100%. The tool does not predict markets.