Investment inputs
These projections assume regular contributions and a steady long-term average return.
Essential Calculator
Investment Calculator
Estimate long-term portfolio growth using a starting balance, recurring contributions, and an expected annual return.
How to use this page
- Enter your starting balance, monthly contribution, annual return, and time horizon.
- Use the chart to see how gains build on top of both the original balance and new contributions.
- Compare conservative and optimistic scenarios before anchoring on one projection.
Results
Ending balance$419,210
Total contributions$154,600
Investment growth$264,610
Y18$419,210
What this calculator helps you see
Investment planning is usually about time, consistency, and reasonable return assumptions. This calculator helps you compare those levers without losing the big picture.
When to use this calculator
Estimate long-term growth
Use this when you want a simple projection for brokerage accounts, general investing goals, or wealth-building plans.
Compare savings rate changes
A higher contribution can sometimes move the outcome more than a slightly different return assumption.
Formula
Future value = starting portfolio growth + contribution growth
The calculator compounds monthly so you can see how ongoing deposits and investment growth reinforce each other over time.
Worked example
An investor starting with $25,000 and contributing $600 per month over 18 years may build a significantly larger portfolio than contributions alone would suggest, especially when growth compounds over time.
| Item | Value |
|---|---|
| Starting portfolio | $25,000 |
| Monthly contribution | $600 |
| Return assumption | 8.5% |
| Timeline | 18 years |
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Before you decide
- Outputs are estimates and should be reviewed against lender or plan-specific terms.
- Inputs are intentionally transparent so assumptions are easy to audit.
- Rates, fees, taxes, and account terms can change the final result.
Page details
- Updated April 15, 2026
- For assumptions and general guidance, see Methodology.
- For how explanatory content is written, see Editorial Policy.
What usually matters most
| Change | Potential effect | Reason |
|---|---|---|
| Start earlier | High | More years for growth to compound |
| Contribute more | High | More capital enters the account regularly |
| Chase small return changes | Medium | Helpful, but often less powerful than time and savings rate |
Common questions
How is this different from the compound interest calculator?
The underlying math is similar, but this page is framed for long-term portfolio planning rather than general interest growth.
Should I use one return assumption or several?
Several. Comparing conservative, base, and optimistic scenarios gives a better sense of uncertainty.