How does the calculator work backward from a goal?
It starts with what you already have. Your current savings are grown at the assumed return, compounded monthly, until the target date; that projected amount is subtracted from the goal to find the shortfall your new deposits must cover.
Next it asks what equal monthly deposit, also growing at the assumed return, would add up to that shortfall by the deadline. That is the sinking-fund formula, the reverse of the future value of a series of deposits. The worked example assumes deposits at the end of each month.
Finally it splits the goal into its sources: what you had already, what you will deposit, and the interest that fills the rest. If your current savings will grow past the goal by themselves, the monthly amount needed is zero.
Gap = G − S × (1 + i)^N Monthly deposit = Gap × i ÷ ((1 + i)^N − 1)
- G
- savings goal
- S
- current savings
- i
- monthly rate (annual return ÷ 12)
- N
- months until the goal
Example: $18,000 for a car in four years
Scenario: Casey wants $18,000 in cash for a car in four years, already has $3,000 set aside, and expects an illustrative 4% annual return in an insured savings account, compounded monthly.
- Monthly rate and months4% ÷ 12 = 0.3333% (0.0033333); 4 × 12 = 48 months
- Growth factor(1 + 0.04 ÷ 12)^48 = 1.173199
- Current savings at the deadline$3,000 × 1.173199 = $3,519.60
- Gap to fill$18,000 − $3,519.60 = $14,480.40
- Monthly deposit$14,480.40 × (0.04 ÷ 12) ÷ (1.173199 − 1) = $278.69
- Where the $18,000 comes from$3,000 already saved + $13,377.12 deposited + $1,622.88 interest
Casey would need to save about $278.69 a month for 48 months to reach $18,000.
If the account's rate drops during the four years, the monthly amount would need to rise slightly to stay on track.
Which goals fit a savings goal calculator?
Planned purchases with a date
A car, a wedding or a move all have a cost and a rough date. Turning them into a monthly figure makes the goal something you can automate.
Irregular bills you know are coming
Insurance premiums, property taxes or holiday spending can be saved for monthly in a sinking fund, so the bill does not land on a credit card.
Checking whether a deadline is realistic
If the monthly amount is more than your budget allows, try a later date or a smaller goal to see which adjustment fits.
Deciding whether to use existing savings
Change the current savings figure to see how much a lump sum from a bonus or refund lowers the monthly amount.
What mistakes throw off a savings goal plan?
Setting the goal at today's price
If you are saving for something whose price will rise, such as tuition or a vehicle, raise the goal to the expected future cost. Otherwise you will be short on the deadline.
Assuming a market return for short-term money
Money you need in a few years has little time to recover from a loss. Using a savings account or CD rate gives a monthly figure you can rely on.
Forgetting taxes on the interest
Interest in a taxable account is taxed each year. On short goals the effect is small, but it slightly increases what you need to deposit.
Skipping months without adjusting
The calculation assumes every deposit is made. If you miss some, rerun the calculator with your updated balance and the months left.
How much does the deadline change the monthly amount?
A lot, especially at the short end. Pushing Casey's deadline from two years to four nearly halves the monthly deposit, from $591.37 to $278.69. Each extra year spreads the gap over 12 more deposits and adds a little more interest.
Notice that the total deposited falls as the deadline moves out, because interest does a bit more of the work. At a 4% rate the effect is modest; the main benefit of a later deadline is the smaller monthly commitment.
| Years to goal | Monthly deposit | Total deposited |
|---|---|---|
| 2 | $591.37 | $14,192.88 |
| 3 | $382.86 | $13,782.96 |
| 4 | $278.69 | $13,377.12 |
| 5 | $216.25 | $12,975.00 |
| 6 | $174.68 | $12,576.96 |
Terms used on this page
- Sinking Fund
- A sinking fund is money you set aside in regular amounts for a specific, expected expense, such as car insurance, holiday gifts or a future car repair. Unlike an emergency fund, which covers surprises, a sinking fund covers costs you can see coming. Spreading them out avoids a budget shock and keeps them off a credit card.
- Compound Interest
- Compound interest is interest earned or charged on both the original principal and the interest that has already built up. Each period's interest is added to the balance, so the next period's interest is a little larger. Over long stretches, compounding makes savings grow faster and unpaid debts grow faster too.
- Emergency Fund
- An emergency fund is cash set aside for unexpected costs or income loss, such as a car repair, medical bill or job gap. It is usually kept in an insured, easy-to-reach savings account. A common target is three to six months of essential expenses, though any starting amount reduces the need to borrow at high rates.
- Savings Rate
- Your savings rate is the percentage of your income that you save rather than spend. It is usually calculated as money saved divided by take-home pay, though some people use gross income. A higher savings rate builds emergency funds faster and shortens the time to reach long-term goals, often more than chasing a higher return.
Savings Goal Calculator: common questions
How much should I save a month to have $20,000 in 4 years?
With nothing saved yet and no interest, it is $20,000 ÷ 48 = about $416.67 a month. Interest lowers that a little: at an illustrative 4% compounded monthly, it is about $384.91 a month. Enter any amount you already have as current savings, since that reduces the monthly figure further.
What is a sinking fund?
A sinking fund is money you set aside in regular amounts for a known future expense, such as a car repair, insurance premium or holiday spending. Instead of paying the bill all at once, you spread it over the months before it is due. This calculator is essentially a sinking-fund calculator: it finds the regular deposit needed to reach a target by a date.
Does interest really reduce how much I need to save?
Yes, but on short goals the effect is modest. In the four-year car example on this page, interest supplies about $1,623 of the $18,000 at 4%. Over longer horizons or with a larger head start, interest covers a bigger share. Most of a short-term goal still comes from your own deposits.
Where should I keep money for a savings goal?
For goals a few years away, many people use insured savings accounts, money market accounts or CDs with terms that end before the deadline. These keep the balance stable and protected up to deposit insurance limits. Longer goals can sometimes take more risk, but losses close to the deadline are hard to recover from.
What if my current savings already cover the goal?
Then the monthly amount needed is zero. If your current savings, grown at the assumed return until the deadline, meet or exceed the goal, no further deposits are required. You might still keep contributing for a cushion, or redirect that money toward another goal. Keep in mind that a projection that just barely clears the goal depends on the assumed rate holding for the whole period.
How do I save for several goals at once?
Run the calculator once for each goal, then add up the monthly amounts. If the total is more than you can save, adjust the deadlines or goal sizes, starting with the least urgent. Keeping each goal in its own labeled account or sub-account makes it easier to see progress. Separate automatic transfers for each goal help too.
Should I count my emergency fund toward a savings goal?
Usually not. An emergency fund is meant to stay available for unplanned costs; if you count it toward a car or trip, you may spend it and be left without a cushion. Size the emergency fund separately and enter only money set aside for this goal as current savings. The emergency fund calculator on this site can help with that separate target.
What happens if I miss a few monthly deposits?
You will end up short unless you make up the difference. The simplest fix is to rerun the calculator with your current balance and the months remaining; it will give a new, slightly higher monthly amount. Alternatively, move the deadline back by the number of months you missed. Either way, catching it early keeps the adjustment small.
Sources
- Compound Interest Calculator — U.S. Securities and Exchange Commission (Investor.gov). Accessed October 17, 2026.
- Deposit Insurance — Federal Deposit Insurance Corporation. Accessed October 17, 2026.
- Topic no. 403, Interest received — Internal Revenue Service. Accessed October 17, 2026.
We cite primary sources: regulators, central-bank data and federal agencies. Worked examples on this page are our own calculations, last checked October 17, 2026. See our methodology.