Sinking Fund Calculator
Work out how much to set aside each month and week to cover a known future expense by its due date with a sinking fund.
How to use this tool
- Enter the total amount the future expense will cost.
- Add anything you have already saved toward it.
- Enter the number of months until you need the money.
- Read the monthly and weekly amounts to set aside.
A sinking fund turns a big future bill into small, regular savings. Enter the total you need, anything already saved and the months until it's due to see your monthly and weekly amount.
Formula
Still to save = Total amount needed − Already set aside (never below $0).
Per month = Still to save ÷ Months until needed.
Per week = Monthly amount × 12 ÷ 52, converting the monthly contribution to a weekly cadence.
How it works
A sinking fund is money you save gradually for a specific, expected expense — annual insurance premiums, holiday gifts, a car repair fund, property taxes, or a planned purchase. Instead of being surprised by a large bill, you break it into small, regular contributions. This calculator divides the amount you still need by the number of months until the due date to give a level monthly figure, then expresses the same amount weekly for those who budget by paycheck or week.
It first subtracts anything you have already set aside, so partial progress lowers the required contribution. The result is a straight-line plan: equal amounts each period, with no assumed interest. Any interest a high-yield account earns is a bonus that lets you finish early or contribute slightly less — we leave it out so the plan is conservative and easy to verify.
The model assumes the target and deadline are fixed and that you contribute evenly. If the expense or timing changes, re-run it with new figures. For multiple goals, run one sinking fund per goal and total the monthly amounts to see your full commitment. Reviewed by the AbraCalc Budgeting Desk for arithmetic correctness and budgeting best practice.
Worked example
$1,200 needed in 12 months, nothing saved yet
- Still to save = $1,200 − $0 = $1,200.
- Per month = $1,200 ÷ 12 = $100.00.
- Per week = $100.00 × 12 ÷ 52 = $23.08.
Set aside per month: $100.00 — about $23.08 per week, with $1,200.00 still to save.
Monthly set-aside to reach $1,200 by horizon
| Months until needed | Per month | Per week |
|---|---|---|
| 3 | $400.00 | $92.31 |
| 6 | $200.00 | $46.15 |
| 12 | $100.00 | $23.08 |
| 18 | $66.67 | $15.38 |
| 24 | $50.00 | $11.54 |
Key terms
- Sinking fund
- Money saved incrementally toward a specific known future expense, so the cost is spread out rather than hitting all at once.
- Target amount
- The full cost of the expense you are preparing for — the figure your contributions must add up to by the deadline.
- Contribution period
- How often you set money aside; this tool shows both a monthly and a weekly figure for the same plan.
- Straight-line saving
- Contributing equal amounts each period, without relying on investment growth, so progress is steady and predictable.
Frequently asked questions
- What is a sinking fund?
- A sinking fund is savings you build up over time for a specific planned expense, such as insurance premiums, holidays or a car repair fund, so the cost does not arrive as a shock.
- How much should I set aside?
- Divide the amount you still need by the months until the deadline. This calculator does that for you and also shows the equivalent weekly contribution.
- Does it assume interest?
- No. It uses a conservative straight-line plan with no assumed return. Any interest you earn in a high-yield account lets you finish early or contribute a little less.
- How is a sinking fund different from an emergency fund?
- A sinking fund is for a known, expected expense with a target and date. An emergency fund is a general reserve for unexpected events and is not tied to a specific purchase.