Sinking Funds: 20 Categories and How to Calculate Them

Most budgets that blow up don't blow up because of a true emergency. They blow up because of a bill everybody knew about: the car insurance premium that renews every six months, the holiday season, the annual registration, back-to-school shopping. These costs aren't surprises. They just don't show up every month, so they never got a line in the budget.

A sinking fund fixes that. You take a known future expense, divide it by the months until it's due, and set that amount aside every month. When the bill shows up, the money is already sitting there. It's one of the least glamorous ideas in personal finance and one of the most effective.

What a sinking fund is

A sinking fund is money you save on purpose for a specific, expected expense. The name comes from corporate finance, where companies set money aside over time to pay off a bond. For a household, it just means a labeled pot of money for a bill you can see coming.

It's different from an emergency fund in one important way. An emergency fund is for things you can't predict: a job loss, a medical bill, a broken transmission. A sinking fund is for things you can. If you use your emergency fund to pay a car registration you knew about in January, the emergency fund isn't there when an actual emergency arrives. Keeping the two separate is the whole point. For the emergency side, see How to Build a $1,000 Emergency Fund.

The sinking fund formula

The math is simple:

Round up. If the math says $87.50, save $90. Bills have a habit of coming in higher than last year. BLS data shows, for example, that prices for vehicle insurance rose 17.4 percent in 2023 alone, so last year's premium is a floor, not a forecast.

If you'd rather not do the division, the savings goal calculator will tell you how much to save each month to hit a target by a date.

20 sinking fund categories to consider

You don't need all of these. Pick the ones that have actually hit your budget in the last year or two. I'd start with three to five, then add more once the first ones feel automatic.

Car and transportation

• Car insurance, if you pay every six or twelve months
• Registration, inspection, and license renewal
• Car maintenance: oil changes, tires, brakes
• A future car down payment or replacement

Home

• Renters or homeowners insurance, if paid annually
• Property taxes, if they aren't in your mortgage escrow
• Home repairs and maintenance
• Furniture and appliance replacement
• Moving costs and a security deposit if you rent

Family and kids

• Back-to-school clothes and supplies
• Kids' activities: sports fees, camp, lessons
• Birthdays
• Child care gaps during school breaks

Health and personal

• Medical and dental deductibles or copays you expect to hit
• Glasses or contacts
• Annual subscriptions and memberships, like warehouse clubs or software

Seasonal and lifestyle

• Holidays and gifts
• Vacation or travel to visit family
• Pet costs: vet visits, vaccines, grooming
• Seasonal utility spikes, like winter heating or summer cooling

A worked example

Here's what a set of sinking funds might look like for a household that starts planning in January. These numbers are invented to show the math.

$330 a month sounds like a lot until you compare it with the alternative: $2,500 in bills arriving in clumps throughout the year and landing on a credit card each time. Spread out, it's a line in the budget. Lumped together, it's debt.

Where to keep sinking fund money

You have a few good options. What matters is that the money is separate from your everyday checking and easy to track.

• One savings account, tracked on paper or in a spreadsheet. Simple and common. You keep a running list of how much belongs to each fund.
• Several savings accounts or "buckets." Many banks and credit unions let you open multiple savings accounts or label sub-accounts at no cost. Each fund gets its own name and balance.
• Cash envelopes. Some people who use cash stuffing keep sinking funds in labeled envelopes. That works for small amounts. For anything large, an insured account is safer than cash at home.

Whatever you pick, use an account with FDIC insurance at a bank or NCUA insurance at a credit union. And don't invest sinking fund money in stocks. A fund due in eight months shouldn't depend on the market being up that week.

What to do if you're starting midyear

You'll almost never start a sinking fund with a full year of runway. Here's how I'd handle the catch-up:

1. List every fund with its real due date, not the ideal one.
2. Do the formula with the months you actually have. A $720 premium due in three months is $240 a month, not $60.
3. If the total doesn't fit, rank the funds by consequence. Insurance and registration lapses cost you more than a smaller holiday budget does.
4. Shrink the flexible ones. Holidays, travel, and gifts can be scaled down to fit. Insurance can't.
5. Next cycle, start on time. Once a bill is paid, start saving for the next one the following month, so you get the full runway.

Common sinking fund mistakes

• Too many funds at once. Fifteen tiny funds you can't keep track of are worse than four you actually use.
• Raiding one fund to cover another. If the holiday fund pays for the car repair, both plans break. Use the emergency fund for actual emergencies.
• Forgetting to update the amounts. Check last year's actual bill before setting this year's total.
• Not counting sinking funds in the budget. The monthly amount is a real expense line. In the 50/30/20 split, I'd put essential ones like insurance under needs and fun ones like vacations under wants. The 50/30/20 Budget Rule Explained covers how the buckets work.

Getting started

1. Pick your three most painful irregular bills from last year.
2. Look up the actual amount and due date of each.
3. Divide by the months remaining and round up.
4. Set up automatic transfers for the day after payday.
5. Write each fund on the bill organizer so the due dates sit next to your regular bills.

Once those three are running on autopilot, add the next one. Within a year, the months that used to wreck your budget will look like every other month.

How sinking funds fit into your monthly budget

The easiest way to think about a sinking fund is as a bill you pay to yourself. Each month, the $36 for registration or the $82 for holidays leaves checking just like your phone bill does. It's spent as far as your monthly budget is concerned, even though it's still sitting in savings.

That framing helps in two ways. First, it stops you from treating sinking fund balances as extra money. The $400 in the back-to-school fund already has a job. Second, it makes the true cost of your life visible. A lot of people think they spend about the same every month, then find that irregular bills add a few hundred dollars a month once they're spread out. That's not a reason to panic. It's the reason those months kept going wrong, and now you can plan for them.

If you use a paper budget, give your sinking funds their own short section under your regular bills. The one-page budget printable guide shows where they fit on the page.