Sinking Fund Calculator

How it works

A sinking fund turns one painful bill into a set of painless monthly set-asides. You know the cost and the date, so the calculator grows anything you have already put aside, then solves for the monthly amount that covers the rest by the deadline, deposits at month end with interest compounding monthly:

• M — the monthly set-aside you are solving for
• G — the total cost of the bill
• P — what you have already put aside
• i — monthly interest rate (annual rate ÷ 12)
• n — number of months until the bill

With the defaults above, funding a $6,000 bill in one year from a standing start at 4% takes about $491 a month. Your own deposits come to roughly $5,891, and interest quietly covers the remaining $109 or so.

✓ Every result is checked against independent reference math. See how we test the calculators →

A worked example: a $6,000 bill one year out

One year out, a $6,000 bill already sits on the calendar, and right now you have $0 set aside for it. Spread across the twelve months, the calculator says $491/month gets you there, with the full amount ready by July 2027.

The mechanics are simple. Twelve monthly set-asides of $491 add up to $5,891 of your own money, and a 4% return on the growing balance kicks in another $109 of interest. Together they land you at exactly $6,000, the whole bill covered without a scramble at the end.

The return you earn barely moves things on a one-year horizon. Parking it in index funds at 7% would trim the monthly ask to $484, while leaving it in cash at 0% raises it to $500, a difference of only $16. Swap in your own bill and deadline to see the monthly set-aside that keeps it stress-free.

Sinking funds worth starting

• Annual insurance and taxes. Car, home, and life premiums or a property tax bill are predictable to the month, so set them aside a twelfth at a time.
• Holidays and gifts. A December of spending is far easier when a small amount has been building since January.
• Car and home upkeep. Tires, servicing, and the appliance that will eventually fail are all known costs waiting for a date.
• Big planned buys. A replacement laptop, a trip, or a wedding deposit all fit the pattern: a known price by a known date.

Running several sinking funds at once

Most households have more than one lumpy bill on the horizon, so the real skill is running a handful of sinking funds together without turning it into a chore. The good news is that they add up cleanly: work out the monthly set-aside for each, then sum them into a single number you save every month.

• List every predictable bill. Insurance renewals, property tax, the holidays, car servicing, and any known replacement all qualify. Writing them down is half the battle, because a forgotten bill is the one that becomes debt.
• Give each a date and a price. Run each through the calculator on its own timeline, since a December gift budget and an annual premium due in March need different monthly amounts.
• Keep them in named buckets. One savings account with clearly labelled sub-accounts, or a simple tracker, lets many funds share a home without their balances blurring together.

Add the monthly figures into one standing transfer and you get the best of both worlds: a single, painless deposit that quietly funds every bill in the background. When one fund is spent, its slice frees up for the next event, so the total tends to stay roughly level across the year rather than spiking each time a bill lands.

A worked example: an annual insurance bill

A classic sinking fund is a yearly premium you would rather not feel all at once. Say your car and home insurance together come to $1,800, due in twelve months, and you are starting from zero with the cash in a high-yield account at 4%. The set-aside works out to about $147 a month, of which your own deposits cover roughly $1,770 and interest quietly handles the last $30 or so.

• Already part-funded. If you had $600 set aside already, the monthly figure would drop to around $96, because that balance grows alongside your deposits and shrinks what is left to cover.
• Round it up. Setting aside $150 instead of $147 builds a small buffer, so a mid-year price rise at renewal does not knock the plan off course.
• Spread the calendar. If several premiums fall in the same month, start their funds earlier or stagger the renewal dates with your insurer, so one heavy month does not land all at once.

When the bill lands, you pay it straight from the fund without touching your everyday money or reaching for a card, and then the same $147 a month begins refilling it for next year. That is the whole appeal of a sinking fund: a bill that used to sting becomes a payment you have already quietly made. Do the same for every recurring bill and the year loses its expensive months entirely, replaced by one steady figure you barely notice.