Investment Growth Calculator
Isolate how one account might grow when you assume a steady return and keep adding the same amount each month. Useful when you do not yet care about tax lots—only trajectory.
Returns are hypothetical; markets vary year to year.
Lump sum + monthly growth
How this is calculated
Month-end balance: earn r = annual ÷ 12, then add the monthly contribution. The lump sum portion compounds as P×(1+r)n; contributions follow the standard annuity future-value factor.
Use this tool for
- Modeling taxable brokerage auto-invest alongside a separate emergency fund.
- Showing a teenager how early monthly savings steepen the curve.
- Stress-testing a lower return assumption before you lock a budget.
Common questions
Why remove the old engine version?
This page now runs the same closed-form math in your browser with no external engine dependency.
Tax drag?
Lower the return field to approximate after-tax compounding in a taxable account.
