Sinking funds: what they are and how to start one
Updated July 22, 2026
A sinking fund is money you set aside a little at a time for a known future expense, so it does not blow up your budget when it arrives. Instead of paying 1,200 dollars for a holiday in December, you save 100 dollars a month starting in January. The cost is identical; the panic is gone.
The name comes from corporate finance, where companies “sink” money into a reserve to retire a bond on its due date. The household version is the same idea at a smaller scale: a known bill, a known date, and steady contributions that meet it.
The math, in one line
Total cost ÷ months until you need it = your monthly contribution.
If you have already saved part of it, subtract that first, then divide what is left by the months remaining. A 1,200 dollar trip with 300 already saved and nine months to go is 900 ÷ 9, or 100 dollars a month.
Two things follow from that formula. Starting early is the cheapest possible move, because months are the denominator. And any month you skip raises every month after it, so a small automatic contribution beats a large intended one.
You can run the numbers in our free sinking fund calculator, which also tells you what your current pace finishes.
How to set one up
- Name the goal and the date. “Holiday travel, December.” Vague funds get raided; named funds do not.
- Estimate the full cost. Round up. An underestimate is a surprise bill with extra steps.
- Divide by the months left. That is your contribution.
- Fund it every month, like a bill. Treat the transfer as non-negotiable.
- Spend it on the thing. When December comes, the money is already there and spending it is the plan working, not a failure.
Sinking fund versus emergency fund
They are not the same thing and should not share an account. An emergency fund covers the unexpected: a job loss, a broken furnace, an urgent trip. A sinking fund covers the expected but irregular: annual insurance, holiday gifts, new tires, a wedding you have been invited to since March.
Mixing them means every predictable expense quietly drains the money you are holding for real emergencies. The full comparison, including which to build first, is in sinking fund vs emergency fund.
What to save for
The best candidates are costs that are certain but do not arrive monthly: insurance premiums, car maintenance and registration, holiday and birthday gifts, travel, home repairs, annual subscriptions, medical deductibles, pet care, and back-to-school. There is a longer, categorized list with typical amounts in sinking fund categories, and guidance on how many to run at once in how many sinking funds should I have.
Where sinking funds fit in a budget
A sinking fund is one line in a larger plan. In envelope budgeting it is simply an envelope that carries its balance forward instead of resetting. In zero-based budgeting it is one of the jobs you give a dollar, sitting alongside rent and groceries rather than competing with them for whatever is left at month end.
That is the real shift. Saving for Christmas in November is a scramble. Saving for Christmas in February is a line item.
How Tuckaway handles sinking funds
In Tuckaway, a sinking fund is an envelope with a goal. You set the target, fund it each month, and a progress bar fills toward the goal while the app calculates how many periods are left at your current contribution. The balance keeps accumulating through month-end rollover instead of resetting, so the fund grows the way a savings account would.
Sinking funds are free and uncapped. There is no bank login, no account, and the numbers stay on your phone.
Common questions
What is a sinking fund?
A sinking fund is money you set aside gradually for a specific expense you know is coming, such as holiday gifts, annual insurance, or new tires. You divide the total cost by the months you have left and save that amount each month, so the bill is already paid for when it arrives.
How do you calculate a sinking fund?
Divide the total cost by the number of months until you need the money. A 1,200 dollar holiday in 12 months is 100 dollars a month. If you have already saved some, subtract that first: remaining cost divided by months left.
Where should you keep a sinking fund?
Anywhere you will not accidentally spend it. A separate high-yield savings account works, as does a labeled envelope in a budgeting app. What matters is that the money is tracked separately from your everyday spending so you can see the balance grow.
Are sinking funds worth it?
They are the cheapest way to handle predictable irregular costs. Without one, a 900 dollar insurance bill either wrecks a month or goes on a credit card. With one, you paid for it 75 dollars at a time and barely noticed.
Put it into practice
Tuckaway is a private envelope budget app. Unlimited envelopes, two-tap logging, and CSV import are free. No bank login.
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