How to use
- Enter the balance you want at the end.
- Enter the annual rate as a percent, the years you have, and any money already saved. Use zero if you are starting from nothing.
- Press Calculate. The hero is the deposit at the end of each month.
- Read the grown-balance line to see what the starting money does by itself.
How it's calculated
The starting balance grows for n months at r = annual rate ÷ 12, with n = years × 12 rounded. Grown = start × (1+r)^n.
The gap is the goal minus that grown amount. The deposit is gap × r ÷ ((1+r)^n − 1). At a zero rate the deposit is the gap divided by n. Deposits are end-of-month.
Worked example
A $20,000 goal in 5 years at 4 percent, starting from zero, needs about $301.66 a month. The starting balance grows to nothing, so the deposits fund the whole goal. If you already have money saved, the grown line shows how much of the goal that pile covers before the deposit is solved.
Assumptions
A constant rate, monthly compounding, and a deposit that does not change. Taxes on interest are not removed. The rate is an assumption you type, not a yield the page promises.
FAQ
What if I already have more than the goal needs?
The deposit is zero and the result says the starting balance covers the goal after it grows.
Does the deposit earn interest too?
Yes. The formula is the future value of an ordinary annuity set equal to the gap, so each deposit compounds until the end.
Is this the same as compound interest?
The compound-interest page projects a balance from a deposit you already chose. This page solves for the deposit that hits a balance you chose.
Should I type my savings-account rate?
Type the rate you want the plan to assume. A higher typed rate lowers the deposit and is only as real as the rate.