Answer two different savings questions
A future-balance calculation asks, “Where might my current routine take me?” A goal calculation reverses the math and asks, “What monthly amount would put a specific target within reach by my deadline?” This tool shows both so a large target does not hide an unaffordable monthly commitment.
Enter the amount you already save each month and inspect the projected balance and goal date.
Enter the target and horizon, then compare the required contribution with your real monthly budget.
Reduce the APY or allow for a missed deposit by rerunning a more conservative case.
APY is already a compounded annual measure
Annual percentage yield reflects the amount of interest an account would earn over a year after taking compounding into account. That is why this calculator does not simply divide APY by 12. It finds the monthly rate that compounds back to the entered APY:
m = (1 + APY)1/12 - 1
End-of-month deposits: FV = B(1 + m)n + C[((1 + m)n - 1) / m]
Beginning-of-month deposits: multiply the contribution term by (1 + m).
B is the current balance, C is the monthly deposit, m is the APY-equivalent monthly rate, and n is the number of months. If APY is zero, future value is B + Cn.
The U.S. Consumer Financial Protection Bureau defines APY in Regulation DD, section 1030.2(c). Use the APY disclosed for the account rather than a promotional label such as “rate” unless the provider confirms they are the same measure.
The transfer date changes the annuity
An end-of-month contribution earns no interest during the month in which it is added. A beginning-of-month contribution is present for that month's growth, so every recurring deposit receives one additional modeled period. This is the distinction between an ordinary annuity and an annuity due.
Do not select “beginning” merely because it produces a larger result. Select it only if the transfer genuinely occurs at the start of each monthly cycle. For irregular pay dates, the estimate is still useful, but the difference between the model and the account will be wider.
How the target solver works
The required-contribution result rearranges the same future-value equation. It first grows the current balance to the deadline, then divides the remaining target gap by the future-value factor for recurring deposits. If the starting balance alone is projected to exceed the target, the required monthly contribution is zero.
The goal-date result takes the opposite route: it keeps your planned monthly deposit and simulates monthly growth until the target is reached. If the goal cannot be reached under the entered combination—such as a zero deposit and a balance that does not grow enough—the result should be read as not reachable under the current inputs, not as a software error.
A worked example with a decision attached
Suppose you have $4,000, transfer $250 at each month's end, earn a constant 4.3% APY, and want $50,000. After 10 years, the model projects roughly $43,332: $34,000 deposited and about $9,332 of interest. The target therefore needs a higher monthly deposit, a longer deadline, or a different target—not a more optimistic APY chosen just to make the result fit.
| Adjustment | What it changes | Trade-off to check |
|---|---|---|
| Increase the monthly deposit | Raises deposits and interest earned on them. | Confirm the amount survives an ordinary month. |
| Extend the deadline | Adds deposits and more compounding periods. | Make sure the purchase date is flexible. |
| Reduce the target | Lowers the required contribution directly. | Reprice the real goal before cutting the buffer. |
| Chase a higher APY | May add interest if the rate lasts. | Check fees, access, eligibility, and deposit coverage. |
Read and export the schedule
The schedule groups the monthly model into annual checkpoints. “Deposits” includes only recurring contributions during that schedule year; the initial balance appears in the starting-balance column. “Interest” is the difference between the ending balance and the money carried in or deposited during that year.
Download the CSV when you want to compare cases in a spreadsheet. Give each file a descriptive name outside the tool—for example, “car-replacement-lower-APY”—because the downloaded numbers only describe the inputs used at that moment. The print view is useful for discussing a household plan, but it remains a projection rather than a bank quote.
Common mistakes that materially change the answer
- Treating today's APY as guaranteed: many savings-account yields are variable and may move several times during the plan.
- Counting money reserved for bills: the starting balance should include only funds actually available for this goal.
- Entering annual contributions as monthly: a $3,000 annual plan is $250 per month only if deposits are evenly distributed.
- Ignoring withdrawals: every withdrawal reduces both principal and the later interest that principal could have earned.
- Optimizing yield before account fit: access rules, minimum balances, fees, and deposit protection can matter more than a small APY difference.
This page is educational. Real balances can differ because APYs move, deposits change, and withdrawals interrupt the compounding path.
Primary sources used for this model
The official U.S. regulatory definition distinguishes annual percentage yield as a measure that reflects interest and compounding over a 365-day period.
Use the FDIC's official guidance to understand coverage categories and limits when evaluating an insured U.S. bank account.
The U.S. Securities and Exchange Commission's investor-education site provides an independent compound-growth reference using an initial amount, recurring contribution, time, rate, and compounding frequency.
Frequently asked questions
APY expresses the total annual yield after the effect of compounding. A stated interest rate may not include that compounding effect. This calculator treats the entered percentage as APY and converts it to an equivalent monthly growth rate.
A beginning-of-month deposit is in the account for one additional monthly growth period compared with an end-of-month deposit. The difference is usually modest over a short horizon but compounds over longer periods.
Yes. Enter a savings goal and time horizon. The required monthly contribution result solves for the level recurring deposit needed under the entered starting balance, APY, and deposit timing.
No. It is a simplified pre-tax projection with one constant APY and regular deposits. Taxes, account fees, withdrawals, missed deposits, and rate changes can make the actual result different.
Choose the next action from the purpose of the money
For an emergency reserve, estimate the target from essential expenses in the emergency fund guide. For money that may remain untouched through market declines, compare the range of outcomes in the investment scenario calculator. Recalculate only after a real change in the goal, balance, transfer, deadline, or account APY.