Free Tool
Sinking Fund Calculator
List every big expense you already know is coming, and get the amount to set aside each month — or each payday — for every one of them. Then see whether the total actually fits the money you have spare, and which funds are behind if it doesn't.
| Fund | Still needed | Months left | Required /month | Required /period | Your plan /month | Fully funded | Status |
|---|
Priority: the funds that are behind
Nothing is behind — every fund reaches its target on time at the contributions you entered.
| Fund | Months left | Required /month | Your plan /month | Short by /month | Fully funded | Slips by |
|---|
| Total still needed across all funds | $0.00 |
| Combined set-aside per month | $0.00 |
| Combined set-aside per period | $0.00 |
| Total annual set-aside (monthly × 12) | $0.00 |
| Amount you have available each month | $0.00 |
| Spare each month | $0.00 |
Assumptions: contributions are plain equal instalments and no interest is added, so the plan is deliberately conservative — if your savings account pays interest you'll arrive slightly ahead. Each fund is treated as separate money; nothing is borrowed from one fund to top up another. "Months left" counts whole months from today, so a bill due part-way through next month counts as 1 and a fund with 0 months left is shown as due now (its whole remaining balance is treated as this month's contribution). Per-payday amounts convert the monthly figure using 12 months, 24 half-months, 26 fortnights or 52 weeks a year — pay cycles differ by employer and country, so pick the one that matches yours rather than assuming four weeks is a month. Each fund is rounded to the nearest cent and the totals are the sum of those rounded amounts, so a total can differ by a cent from the unrounded arithmetic. The annual figure is your combined monthly set-aside × 12; funds that finish part-way through the year will actually cost less than that over 12 months. Amounts are formatted in US dollars for display only — the arithmetic is identical in any currency.
How much should you put in each sinking fund every month?
A sinking fund is money set aside gradually for an expense you already know is coming: the car service, the annual insurance renewal, Christmas, the holiday you've booked, school fees, the vet's yearly visit, the laptop that will need replacing. None of these are emergencies. They are just bills that arrive rarely enough to feel like a shock when they do, and a sinking fund is how you stop them landing on a credit card.
The arithmetic is deliberately plain: (target amount − what you've already saved) ÷ whole months until you need it. A $900 car service six months away with $150 already put aside needs (900 − 150) ÷ 6 = $125 a month. That's it. Many "sinking fund calculators" online are really bond-amortisation tools that compound an interest rate into the answer — useful in corporate finance, but for a savings pot you'll drain in eight months, interest is a rounding error, and building your plan around it just makes the number harder to trust. This calculator leaves it out and tells you so, which means the figure it gives you is a floor rather than an optimistic projection.
The part most single-fund calculators miss is that nobody has one sinking fund. You have five or six, all running at once, and the number that decides whether the plan survives contact with real life is the combined monthly total against the money you actually have spare. Four modest funds at $125, $100, $200 and $150 a month are all individually reasonable and add up to $575 — which is a problem if your budget has $500 in it. Working them out one at a time hides that; working them out together is the whole point.
When the total doesn't fit, you have four honest choices, and only four: push a deadline back, lower a target, drop a fund, or knowingly underfund one and top it up from income when the bill arrives. Enter a smaller figure in the "your plan" column for any fund and the calculator shows when that fund would actually be full, and how many months past your deadline that is. The priority table lists everything that's short with the nearest deadline first, because a $30 monthly gap on something due in two months matters far more than a $200 gap on something due in three years.
Two practical notes. Keep sinking funds somewhere separate from your day-to-day account — a second savings account, or several, so the balance you see is genuinely spare. And re-run the numbers whenever a target changes: quotes go up, dates move, and a plan built on last year's insurance premium quietly stops working.
Frequently asked questions
What is a sinking fund?
A sinking fund is money you set aside a bit at a time for a specific expense you already know is coming — an insurance renewal, a car service, Christmas, a holiday, school fees, a replacement laptop. Because the expense has a known cost and a known date, you can divide it into equal monthly amounts instead of being surprised by it and reaching for a credit card.
How do I calculate how much to put in a sinking fund each month?
Take the target amount, subtract whatever you have already saved for it, and divide what's left by the number of whole months until you need the money. A $900 car service in 6 months with $150 already put by works out at (900 − 150) ÷ 6 = $125 a month. Do that for every fund and add the monthly amounts together to get your total set-aside.
What should I do if my sinking funds add up to more than I can afford?
You have four honest options: push a deadline back, lower a target, drop a fund entirely, or deliberately underfund one and top it up from income when the bill arrives. The priority table in the calculator shows which funds are short and by how much, sorted with the nearest deadline first, so you can see which decision is most urgent rather than spreading the pain evenly.
Is a sinking fund the same as an emergency fund?
No. A sinking fund is for an expense you can name and date; an emergency fund is an untouched buffer for the things you can't predict, like a job loss or a boiler failing. Spending a sinking fund is the plan working. Spending an emergency fund means something went wrong, and most people want to keep the two pots separate so they can tell the difference.
Want the full system, not just this one number?
This calculator works out today's set-aside amounts and forgets them the moment you close the tab. The Personal Budget & Debt Payoff Planner is a spreadsheet system that keeps your sinking funds alongside a full monthly budget — so you can log what you actually transferred each month, watch each fund's balance grow against its target, and see the set-aside sitting inside your real income and expenses rather than in a separate calculator.
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