Solving the future-value annuity for the payment gives
PMT = Goal × r / ((1+r)n − 1)
with r the monthly rate and n the number of months. Deposits are assumed at month-end.
Frequently asked questions
Do deposits earn interest immediately?
This calculator assumes month-end deposits, so each deposit earns interest starting the following month — the conservative standard assumption.
What rate should I use?
Use the APY of your savings account or money-market fund. For long horizons, a diversified portfolio has historically returned more — but returns are not guaranteed.