Savings Goal Calculator
How it works
Current savings are projected forward on their own first: currentSavings · (1+r)ⁿ, where r is the monthly return and n the number of months. If that alone already reaches the goal, the required deposit is zero. Otherwise, the remaining shortfall — the goal minus what current savings grow to by themselves — is divided by the same annuity factor the Retirement Savings Calculator uses to grow a monthly contribution, ((1+r)ⁿ − 1) / r, but inverted: instead of asking what a deposit grows to, it asks what deposit grows to a given amount.
Total contributed adds up current savings plus that deposit over every month; total growth is whatever the reached balance ends up being above that — the part that came from compounding rather than from money you put in yourself.
Frequently asked questions
What if I'm already on track to hit my goal?
If your current savings alone are projected to reach (or pass) the goal by compounding on their own, the required monthly deposit comes back as $0 — that is not an error, it just means no further contribution is needed to get there on the timeline you gave.
Why compound monthly rather than yearly?
A monthly deposit compounding yearly would have to assume every month's deposit landed at the start of the year (overstating growth) or the end (understating it). Compounding monthly, in step with the deposits themselves, avoids picking either wrong assumption.
How does this relate to the Retirement Savings Calculator?
They solve the same equation for opposite unknowns. Retirement Savings asks "what does a monthly contribution grow to?" — this asks "what monthly contribution is needed to reach a target?" Use this one to find the deposit a goal requires, then check it against the Retirement Savings Calculator to see how sensitive that deposit is to a more optimistic or conservative return assumption.