Sinking Funds: What They Are and How to Set Them Up

Sinking funds are small pots of savings you fill a little each month for a cost you know is coming, such as a car insurance renewal, holiday gifts or a summer trip. To size one, subtract what you have already saved from the goal and divide by the months until you need the money. When the bill arrives the cash is waiting, so it does not land on a credit card or wreck that month’s budget.

Below: a plain definition, how a sinking fund differs from an emergency fund, the formula, where to keep the money and a worked setup for three funds.

What Is a Sinking Fund?

A sinking fund is money you set aside on a schedule for one specific, expected expense. The name comes from business finance, where a company puts money away over time to repay a bond. At home the idea is the same: many small payments now instead of one large one later.

The costs that suit a sinking fund have three things in common:

• You know it is coming. A registration renewal, a birthday, a dental visit, a trip.
• It is not monthly. Rent and the phone bill already live in your monthly budget.
• It is big enough to hurt. A $12 annual fee can come out of the month it lands in. A $1,260 insurance premium usually cannot.

Holiday gifts, an annual premium and new tires are all predictable, yet they feel like emergencies when nothing was set aside. A sinking fund moves them into the plan, one month at a time.

Sinking Fund vs Emergency Fund

Both are savings, but they do different jobs. Mixing them is how an emergency fund ends up paying for the holidays and is half empty when the car breaks down.

	Sinking fund	Emergency fund
Covers	A known, planned cost	Something you cannot plan: a job loss, an urgent repair, a medical bill
Amount	Set by the cost, such as a $1,260 premium	Set by your monthly expenses and how many months you want covered
Due date	Yes, or a regular cycle	None
When you spend it	On schedule, every cycle	Rarely
Afterward	Start saving for the next cycle	Rebuild it to your target

Keep them apart, even if both sit at the same bank. If a predictable cost comes out of the emergency fund, that fund is smaller on the day something truly unexpected happens.

The Sinking Fund Formula

Monthly amount = (goal minus what you have already saved) ÷ months until you need it

The calculator on our sinking funds tracker page opens with a $1,200 goal, $150 already saved and 10 months to go. That is ($1,200 minus $150) ÷ 10 = $105 a month.

Three habits keep the formula honest:

1. Count contribution months, not the gap between dates. Start in October for a bill due in June and you contribute in October through May: 8 months, not 9.
2. Round up. If the math gives $64.29, save $65 so the fund is full on time rather than a few dollars short.
3. Recalculate after a missed month. The formula uses what is left and the months left, so running it again gives you the new amount straight away.

To do this in Google Sheets or Excel, put the goal in B2, the amount saved in C2 and the due date in D2. The same formulas work in both apps:

• Months left, counting this month (E2): =(YEAR(D2)-YEAR(TODAY()))*12+MONTH(D2)-MONTH(TODAY())
• Monthly amount, rounded up to whole dollars (F2): =ROUNDUP((B2-C2)/MAX(1,E2),0)

If you are paid every two weeks, multiply the monthly amount by 12 and divide by 26 for a per-paycheck figure. Our guide on how to budget biweekly paychecks shows where those transfers fit around your bills.

How to Set Up Sinking Funds

1. Pull the last 12 months of statements. Search your bank and card statements for anything that was not a monthly bill: renewals, repairs, gifts, travel, school costs.
2. Write each cost with an amount and a month. “Car insurance, $1,260, June” is enough.
3. Pick your first three to five funds. Start with the largest costs due soonest. Our list of sinking fund categories will jog your memory for the ones statements miss.
4. Label each fund dated or ongoing. A dated fund has a due date, like a premium or a trip. An ongoing fund covers costs that happen every year at unknown times, like car repairs or vet visits. Size an ongoing fund as last year’s total divided by 12 and keep paying in.
5. Work out each monthly amount with the formula above.
6. Add one savings line to your monthly budget for the total. In a zero-based budget, this is one more job for your dollars.
7. Schedule the transfer for payday, so the money moves before it can be spent.
8. Pay the bill from the fund when it comes, then set the goal for the next cycle.

If you have kids, plan on a few funds for school costs, activities and birthdays. The family budget guide covers those categories.

Where to Keep Sinking Fund Money

You will need this money on a known date, so keep it somewhere separate from everyday spending, easy to reach within a day or two, and where the balance cannot drop. Anything whose value moves up and down is a poor fit for a bill due in six months.

Option	How it works	Watch out for
One savings account for all funds	Every fund shares one balance, and a tracker shows how it splits	Without the tracker you cannot tell which money belongs to which fund
One account or sub-account per fund	Each fund has its own balance, where your bank offers this	More accounts to manage and more transfers each payday
Cash envelopes	Small funds sit in labeled envelopes at home	Loss or theft, and it only suits small amounts
Left in checking	The money stays put and you track it on paper	Very easy to spend by accident

One separate savings account plus a simple tracker is the easiest setup to keep running. You get one transfer per payday and one place to look.

Worked Example: Three Sinking Funds

Here is a setup made in late September 2026, with contributions starting in October. All amounts are example numbers.

Fund	Type	Goal	Already saved	Due	Months to save	Monthly amount
Car insurance (annual premium)	Dated	$1,260	$180	June 2027	8 (Oct to May)	$135
Summer trip	Dated	$1,350	$0	July 2027	9 (Oct to Jun)	$150
Car maintenance and repairs	Ongoing	$960 a year	$0	None	Every month	$80
Total						$365

The math: ($1,260 minus $180) ÷ 8 = $135, $1,350 ÷ 9 = $150, and $960 ÷ 12 = $80.

That is $365 a month. Paid every two weeks, it works out to $365 × 12 ÷ 26 = $168.46, so $169 per paycheck. Paid weekly, it is $84.23, so $85 a week.

Now follow the funds through the year:

• A missed month. Say December is tight and you skip the car insurance transfer. In January you have $450 saved ($180 plus two payments of $135), $810 to go and five months left, January to May. The new amount is $810 ÷ 5 = $162 a month.
• A draw on the ongoing fund. From October to March the maintenance fund collects 6 × $80 = $480. A $430 brake job in April leaves $50, and the $80 a month keeps going. No card, no scramble.
• The next cycle. Once the premium is paid in June, the next one is due in June 2028, a full 12 months away. The same $1,260 now needs only $1,260 ÷ 12 = $105 a month, $30 less than the first round. The first year of any dated fund costs the most because you are catching up.

Tracking Sinking Funds in a Spreadsheet

One row per fund is enough: goal, amount saved, due date, monthly amount and amount left. Every time you move money, record it twice: as a contribution to the fund, and as savings in that month’s budget, so the budget knows the money is spoken for.

The sinking funds tab in our budget spreadsheet works this way. You set a goal and a monthly goal for each fund and log contributions, and it shows the amount left, progress, months left and an estimated finish date. It sits apart from the monthly tabs, so each transfer also goes in your monthly budget as savings.

Set up your first fund this week: take the next non-monthly bill on your calendar, run the formula, and schedule the transfer for your next payday.