The Portfolio Growth Calculator projects an investment balance from a starting value, recurring contributions, expected return, and time horizon. It separates the final balance into money contributed and estimated investment growth. The calculation uses monthly compounding and assumes contributions are made at the end of each month. Because actual returns vary, the result is best used for scenario planning rather than as a forecast of guaranteed performance.
Use the amount already invested at the start of the projection.
Enter the amount expected at the end of each month.
Use a rate appropriate for the scenario and test more than one case.
Enter the number of years contributions and compounding continue.
Review how much of the ending value comes from contributions versus estimated returns.
Monthly rate = (1 + annual return)^(1/12) − 1
Each month: ending balance = previous balance × (1 + monthly rate) + monthly contribution
The model assumes end-of-month contributions and a constant return.
Use the result as an estimate based on the values and assumptions entered.
Changing an input updates the result automatically.
Given: $25,000 starting balance, $750 monthly contribution, 7% annual return, and 20 years.
Calculation: Convert 7% to its monthly equivalent, compound the existing balance each month, and add $750 at the end of every month for 240 months.
Result: The projected ending balance is approximately $506,000, depending on rounding.
No. It is a scenario input, and actual returns can be higher, lower, or negative.
The calculator assumes end-of-month contributions.
No. Reduce the return assumption or model those costs separately.
Yes, as long as it is greater than -100% annually.
A range shows how sensitive the outcome is to an assumption that cannot be known in advance.