How this number is made
A finance calculator answers whichever time-value input you do not know. This one solves for the return, the monthly deposit, or the years, with monthly compounding. Ending balance, when you already know every input, is the compound-interest page. The rate is constant, which a real portfolio is not.
- Pick what you are solving for. The other numbers are the ones you already decided.
- The starting balance can be zero if you are starting from contributions only.
Formula
Balance after n months at monthly rate r is principal × (1+r)^n + deposit × ((1+r)^n − 1) ÷ r. The page solves that equation for r, for the deposit, or for n.
Worked example
With the figures already in the form, annual return required is 5.68%.
Questions
Why might the return say it cannot be solved?
The goal is above what even a very high return produces, or the starting balance already overshoots at a deeply negative return. Change the goal or the contributions.
Can the deposit come out negative?
Yes. That means the starting balance grows past the goal with no new money, so the “deposit” is really a withdrawal.