Compound Interest Calculator
Project a balance with principal, monthly contributions, annual rate and time.
Project compound growth with monthly contributions
Estimate a future balance from starting principal, monthly additions, annual rate and years.
Assumes monthly compounding and contributions made at the end of each month. It is a mathematical scenario, not a return forecast.
How this compound-interest scenario works
The calculator applies one-twelfth of the entered annual rate each month, then adds the monthly contribution at the end of that month. The final balance is separated into your total contributions and mathematical growth.
How to use it
- Enter the amount you start with.
- Add a recurring monthly contribution, or use zero.
- Enter an annual rate for the scenario you want to model.
- Choose the time horizon and compare final balance with contributions.
A rate input is not a prediction
Actual investment returns are uncertain and can be negative. Savings products may also use different compounding and crediting conventions. Treat the rate as a mathematical assumption only.
Contribution timing changes results
This implementation assumes contributions arrive at the end of each month. Contributions made at the beginning of a period would compound for slightly longer and produce a different result.