Sinking Fund Calculator
Add every irregular expense and savings goal, set a target and a timeline for each, and see exactly how much to set aside every month — so the bill is never a surprise.
Your Sinking Funds
How the sinking fund math works
Find the gap
For each fund, subtract what you've already saved from the target. That remaining gap is all you still need to set aside before the expense arrives.
Spread it over the runway
Divide that gap by the number of months until you need it. The calculator uses (target − saved) ÷ months so the money is ready right on time.
Add up every fund
Sum the per-fund monthly amounts into one number. That total is what you budget each month — fund it once and every irregular expense is handled. See how to set up sinking funds.
Sinking funds work best inside an envelope budget → — each fund is just a named envelope you top up every month. Need ideas? Browse common sinking fund categories →
Stop scrambling for irregular bills
LazeeFish is $5/month and turns every sinking fund into a named envelope that funds itself each month.
Start free trial — no credit cardWhat is a sinking fund?
A sinking fund is money you set aside a little at a time for a specific, known expense that doesn't show up every month — annual insurance, the holidays, property taxes, a new phone, or a vacation. You know roughly how much it'll cost and roughly when, so instead of getting blindsided you spread the cost across the months leading up to it.
The reason monthly contributions beat scrambling is simple: an $1,800 insurance renewal feels brutal as a single hit, but at $200 a month over nine months it's just another line in your budget. Smoothing lumpy costs into steady monthly amounts is the entire point — it keeps surprise bills from blowing up your month or draining your emergency fund.
The math is the same for every fund: take the target amount, subtract anything already saved, and divide by the months until you need it. (target − saved) ÷ months. The calculator above runs that for each row and adds the results into one total — the single number to fund each month so nothing catches you off guard.
Sinking funds pair naturally with the envelope method: each fund is just a named envelope you top up on payday, and the balance grows visibly until the bill comes due. For a list of expenses worth a fund, see common sinking fund categories, or read the full walkthrough on how to start sinking funds.
Calculator FAQ
What is a sinking fund?
A sinking fund is money you set aside a little at a time for a specific, known expense that doesn't recur monthly — like annual car insurance, the holidays, a new laptop, or property taxes. Instead of scrambling when the bill lands, you spread the cost across the months leading up to it so the cash is already there.
What's the difference between a sinking fund and an emergency fund?
A sinking fund is for expenses you can see coming — you know the amount and roughly the date, so you save toward a target. An emergency fund is for the things you can't predict, like a job loss or a surprise medical bill, and it usually targets 3–6 months of expenses with no set spend date. Sinking funds keep unexpected-but-foreseeable costs from ever touching your emergency fund. Sizing the latter? Use the emergency fund calculator.
How many sinking funds should I have?
As many as you have distinct irregular expenses — there's no magic number. Most households land between 4 and 12: insurance, holidays, car maintenance, medical, travel, gifts, annual subscriptions, and so on. The point isn't more accounts; it's that every predictable lump has a named bucket so it never becomes a surprise. See common sinking fund categories for ideas.
Where should I keep my sinking fund money?
For funds you'll spend within a year or two, a high-yield savings account keeps the money safe, liquid, and slightly growing — investing it risks a downturn right when you need to spend. You don't need a separate bank account per fund; one account plus envelope-style tracking lets you see each fund's balance without juggling logins.
How do I calculate the monthly contribution for a sinking fund?
Take the target amount, subtract anything you've already saved, then divide by the number of months until you need it: (target − saved) ÷ months. A $1,800 insurance bill due in 9 months with $0 saved is $200/month. Repeat for each fund and add the monthly figures together — that total is what you set aside each month.
Also see: Savings calculator · Emergency fund calculator · 50/30/20 budget calculator