What is a sinking fund? Examples, math, and how to start
Car registration isn't an emergency. You knew it was coming. A sinking fund turns it into a small number you never think about again.
What a sinking fund is
A sinking fund is money you set aside a little at a time for one specific cost you know is coming. It has three parts: a target (how much), a date (when), and a monthly amount (what it takes to get there).
When the bill arrives, the money is already sitting there. The month it lands in looks like any other month.
Why ‘surprise’ costs aren’t surprises
Holiday gifts happen in December every year. Car registration comes on the same date every year. The annual renewal on that app you use shows up when it did last time.
These costs feel like emergencies because they don’t show up in a normal month. Then one month they all show up at once, and a $600 December wipes out what should have been savings.
A sinking fund spreads that cost back across the months before it, where it’s small enough to not notice.
The one formula you need
- Target
- $600
- Already saved
- $0
- Still needed
- $600
That’s it. (Target − already saved) ÷ months left = monthly amount. If the number looks too big, you have two honest levers: a smaller target, or more months (by starting earlier next time).
Sinking fund examples
Three common ones, with real-looking numbers:
| Fund | Target | Months left | Per month |
|---|---|---|---|
| Car registration | $240 | 8 | $30 |
| Holiday gifts | $600 | 10 | $60 |
| Annual app renewals | $120 | 12 | $10 |
| Total | $960 | $100 |
$100 a month, set aside before spending, means $960 of “surprises” stop being surprises. Other good candidates: next fall’s tuition, a friend’s wedding, a trip home, a new phone when the current one is on its last legs.
Sinking fund vs emergency fund
They both hold money for later, but they do different jobs:
- Sinking fund: known cost, known date. Tuition in September. Gifts in December.
- Emergency fund: unknown cost, unknown date. A burst pipe. A gap between jobs.
Keeping them separate protects both. If holiday gifts come out of your emergency fund, it isn’t there when the real emergency shows up. And if you can see that December is already covered, you won’t be tempted to dip into the money meant for the unexpected.
Starting late
Found out about sinking funds in October, with gifts due in December? You’re not behind. You’re just starting with fewer months.
Run the formula with the months you have. If $600 ÷ 2 months is more than you can set aside, lower the target to something that fits, and start next year’s fund in January. Every month you add makes the monthly number smaller.
How SaveFirst does it
In SaveFirst, every goal and sinking fund gets its own bucket with a target, a due date and a percentage complete. Each one is funded every month as part of saving first, before your spendable balance is worked out.
So instead of a vague sense that December will be expensive, you see something like Holiday gifts: $360 of $600, 60%. Next to it, your emergency fund keeps growing separately. Then you stop thinking about it.
Frequently asked questions
What is a sinking fund in simple terms?
A sinking fund is money you set aside a little at a time for a specific cost you know is coming, like car registration or holiday gifts. When the bill arrives, the money is already there.
What's the difference between a sinking fund and an emergency fund?
A sinking fund is for a known cost on a known date. An emergency fund is for costs you can't predict, like a sudden repair or a gap in income. Keeping them separate means a planned bill never drains your emergency money.
How many sinking funds should I have?
One for each known cost that would otherwise knock a normal month off course. Starting with two or three is easier to keep up than starting with ten. Add more once the first few feel automatic.
Do sinking funds need separate bank accounts?
Not necessarily. Where you keep the money is your call. What matters is that each fund has its own target, date and monthly amount, so you can see what's covered at a glance.
This article explains a method for thinking about money. It isn’t financial, tax or legal advice, and it doesn’t tell you what to do with your money.