Orbit
HomeDealsBlog
Resources
ToolsCancel HubSubscription DealsCompareNews
Get Started →
Savings calculator

Sinking Fund Calculator

Add the costs you can see coming, Christmas, car service, insurance, a holiday, and see what to set aside each month for each one. The tool totals them into the single amount to move into savings. Free, no signup.

Multiple goals at onceAny currencyMonthly total to budget
Your sinking funds
£
£
£
£
£
£
Set aside each month
£260
Split across 3 funds building to a combined £2,550. Next up: Christmas, in 5 months.
46%
15%
38%
Christmas £120/moCar service & MOT £40/moSummer holiday £100/mo
Each fund
Christmas
£600 to go over 5 months
£120/mo
On track
Car service & MOT
£360 to go over 9 months
£40/mo
On track
Summer holiday
£1,200 to go over 1 year
£100/mo
On track
Monthly total
£260
Combined target
£2,550
Still to save
£2,160
Funds funded
0/3
Christmas lands around December 2026. Each monthly figure is the remaining cost divided by the months left, so the total is what to move into savings every month.
Assumes level monthly saving and no interest earned. A guide, not financial advice.
Simon Chadwick
Simon Chadwick
Founder, Orbit Money
Method: cost minus saved, divided by months to goUpdated: 16 July 2026Sources: MoneyHelper, Investopedia

What is a sinking fund?

A sinking fund is money you build up gradually for a specific future cost you already know is coming. The idea is old, companies use sinking funds to set aside money to repay a bond, but for a household it is simpler. You have expenses that do not arrive every month yet are entirely predictable: the car service, the insurance renewal, the December splurge, next summer’s holiday. Left to chance, each one feels like a surprise and often ends up on a credit card. A sinking fund turns that lump into a small, steady monthly amount you barely notice.

How to calculate a sinking fund

The maths is short. Take the total cost, take away anything you have already saved towards it, and divide what is left by the number of months until you need it. That is your monthly set-aside. A £600 Christmas five months away with nothing saved is £120 a month. A £450 car service nine months away with £90 already put by is £360 over nine months, so £40 a month. The calculator above runs this for every goal you add and sums the results, so the headline figure is the total to move into savings each month.

Common sinking fund categories

Most people find the same handful of costs are the ones that catch them out. Give each its own pot:

Sinking fund or emergency fund?

They do different jobs. A sinking fund is for a cost you can name and date, so it fills up and empties on a schedule. An emergency fund is for the unexpected, so it sits as a buffer you hope never to touch. Build the emergency fund first, since it covers the genuine shocks, then layer sinking funds on top for the planned lumps. Together they mean neither a surprise nor a known bill has to go on credit.

How to use this calculator

  1. Add each goal with its total cost and, if you have started, the amount already saved.
  2. Set when it is due, either a target date or the number of months away.
  3. Read the monthly figure for each fund and the total to set aside across all of them.
  4. If the total is too high, push a date out or trim a target until the monthly amount fits your budget.

Frequently asked questions

What is a sinking fund?
A sinking fund is money you set aside a little at a time for a known future expense, so the bill does not land as a shock. Christmas, a car service, an annual insurance renewal, a holiday or a new phone are all typical examples. You know roughly what each will cost and roughly when, so you divide the cost by the months until it is due and save that amount every month. By the time the expense arrives, the money is already there and nothing goes on a card.
How do you calculate a sinking fund?
Take the total cost of the thing you are saving for, subtract anything you have already put aside, then divide what is left by the number of months until you need it. A £600 Christmas with nothing saved and five months to go is £600 divided by 5, so £120 a month. A £450 car service with £90 already saved and nine months away is £360 divided by 9, so £40 a month. The calculator above does this for every goal at once and adds up the monthly figures, so you see the single amount to move into savings each month.
What is the difference between a sinking fund and an emergency fund?
A sinking fund is for a planned expense you can see coming, with a known cost and date, such as car tax or a wedding you are invited to. An emergency fund is for the unplanned, a boiler that fails or a sudden loss of income, so it has no target amount tied to one bill and no date. Most people keep both. The emergency fund sits untouched as a buffer, while sinking funds fill up and empty as each planned cost comes and goes.
What sinking fund categories should I have?
Start with the costs that reliably catch people out once or twice a year: Christmas and gifts, car costs (service, MOT, tyres, tax), insurance renewals, holidays, home repairs and medical or dental bills. Add anything specific to you, a pet, school costs, a phone or laptop upgrade, an annual subscription that renews in one lump. The point is to name each recurring lumpy cost and give it its own pot, rather than hoping one general savings balance covers everything.
How much should I put in a sinking fund each month?
Enough that the pot is full by the time the expense is due. Divide the remaining cost by the months you have left and save that. If several funds together add up to more than you can spare each month, push the less urgent dates further out, trim the target amounts, or drop a category for now. The calculator shows the running total across every fund, so you can adjust the goals until the monthly commitment fits your budget.
Where should I keep my sinking funds?
A separate savings account, ideally one that lets you label pots or hold several sub-accounts, keeps sinking fund money away from your everyday balance so you do not spend it by accident. Many app-based banks let you create named pots for exactly this. Interest is a bonus rather than the goal here, since the money is usually spent within a year, so easy access matters more than the rate.

Related tools

50/30/20 Budget Calculator
Fit your sinking funds into needs, wants and savings.
Emergency Fund Calculator
Work out the buffer that covers the unplanned costs.
Compound Interest Calculator
See how longer-term savings grow with interest.
Debt Payoff Calculator
Clear what you owe with the snowball or avalanche method.
How Long Will My Money Last?
See how long your savings stretch when you draw on them.

More budgeting & savings calculators

Superannuation Calculator
Estimate your super balance at retirement from your salary and current balance, in today's dollars. 12% Super Guarantee.
Net Worth Calculator
Add up what you own, subtract what you owe, and see your net worth in one number, with an indicative benchmark for your age.
Mortgage Overpayment Calculator
See how much interest you'd save and how many years you'd knock off your mortgage by overpaying each month or with a lump sum.
Monthly vs Annual Calculator
Compare monthly vs annual pricing, see your potential savings, and factor in promo discounts.
Fuel Cost Calculator (AU)
Work out the petrol or diesel cost of any trip from distance, fuel use and pump price. See cost per km, plus weekly and yearly commute totals.
Interest-Only Mortgage Calculator
Work out your monthly interest-only payment, the total interest over the term, and the capital still owed at the end. Compare it with a repayment mortgage.

Sinking funds cover the bills you see coming. Orbit catches the ones you forgot.

Orbit finds every subscription and recurring charge draining your account, so the money you save has fewer leaks to plug.

Try Orbit free
Simon Chadwick
About the author
Simon Chadwick
Founder of Orbit Money

Simon is the founder of Orbit Money, a tool that helps people track subscriptions and recurring spend. He builds Orbit's free money calculators and writes about personal finance for readers in the UK, Australia and beyond.

More from Simon →
This tool is a guide, not financial advice.