Sinking Fund Calculator
List your irregular expenses, what each costs, and when it's due. You'll get the monthly slice for every bill and the single set-aside amount that covers them all.
List each irregular expense, what it costs, and how many months until it's due. The slice is what to set aside monthly.
Total monthly set-aside
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Enter an amount and months for any row
Biggest single slice
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Covered per year
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Predictable is not the same as monthly
Most budgets fail in the months that were never average. December is the classic: gifts, travel, and year-end bills all land at once, and a budget built on the typical month calls it a crisis. But nothing about December is a surprise; it happens every year at the same address. The sinking fund's whole insight is that predictable-but-lumpy expenses can be flattened into monthly ones by dividing early. Our sinking funds guide covers the full method, and zero-based budgeting shows where the slices fit in a monthly plan.
Where the slices live
A sinking fund is a practice, not a product: any savings account can hold it. A high-yield savings account is the natural home since the car-insurance money sits for six months and may as well earn something on the way. The mechanics matter less than the labeling: whether it's separate accounts, one account with a spreadsheet, or named buckets in an app, each dollar needs a job title. Unlabeled savings has a way of becoming general-purpose money that the next impulse spends.
Goals that run themselves
The math on this page is the same future-with-a-deadline pattern as any savings target, which is why the savings goal calculator feels familiar. It's also the pattern goals in Stoia run natively: name the expense, set the amount and date, and the monthly pace is computed and tracked against your real balances, so a fund falling behind is visible in March rather than discovered in November. Until launch, this calculator plus one recurring transfer gets you most of the way there.
Frequently asked questions
What is a sinking fund?
A monthly set-aside for a specific expense you know is coming: insurance premiums, holiday gifts, a vacation, car registration. Divide the cost by the months until it's due and save that slice each month, so the bill arrives pre-paid instead of as a budget emergency.
How is a sinking fund different from an emergency fund?
Sinking funds are for known expenses with rough dates; the emergency fund is for genuine surprises like a job loss or an ER visit. Keeping them separate protects both: December gifts shouldn't drain the job-loss cushion, and a transmission failure shouldn't raid the vacation money.
Where should I keep sinking funds?
A high-yield savings account is the usual home: the money earns interest while it waits, and it's reachable when the bill lands. Some people open one account per fund; most keep a single savings account and track the buckets on paper or in an app.
How many sinking funds should I have?
Start with the few bills that actually wreck months: insurance paid annually or semi-annually, holidays, travel, car maintenance, and annual subscriptions are the usual suspects. Five well-chosen funds beat fifteen abandoned ones; you can always add more once the habit sticks.
What if the bill arrives before the fund is full?
Pay the gap from flexible spending that month and keep going. A fund that's 70% full still turned a $600 shock into a $180 one. The goal is shrinking surprises, not perfection, and next year's version of the same bill starts fully funded on January's schedule.
Does this calculator save my numbers?
No. Everything runs in your browser and disappears when you leave. Nothing is uploaded or stored.
Want this to update itself?
Stoia connects your real accounts and keeps the full picture current: net worth, budgets, and goals. Launching in 2026.