Interactive financial calculator
Sinking Fund Calculator
Calculate the weekly, biweekly, or monthly contribution needed for a planned expense by a chosen date or number of months.
- Free to use
- No account required
- Inputs stay in your browser
Methodology & Assumptions
How this estimate is calculated
Formula: required contribution = [target − current balance × (1 + periodic rate)periods] ÷ future-value annuity factor. APY is converted to an effective rate for the selected frequency, and contributions occur at period-end. At 0% APY, the remaining gap is divided evenly across contribution periods.
Illustrative result: figures are rounded for display after calculations use full numeric precision. Actual results may differ.
Currency: dollar symbols are a display convention. Enter every monetary amount in one consistent currency; the calculator does not convert currencies or apply jurisdiction-specific tax rules.
How to Use This Sinking Fund Calculator
Enter a target amount, current balance, target date or months remaining, contribution frequency, and optional APY. Use the optional goal label only for the current page display; it is not placed in URLs, analytics, canonical tags, or structured data.
A monthly sinking fund calculator is useful for planned insurance, repairs, annual bills, replacement purchases, or travel. For unexpected essential costs, use the Emergency Fund Calculator and review How Much Emergency Fund Do I Need?
What a Sinking Fund Is
A sinking fund is money set aside gradually for a known future expense, such as an annual insurance bill, planned repair, replacement purchase, or travel budget. Unlike an emergency fund, it is intended for a reasonably predictable cost. Unlike a general savings goal, it usually repeats or has a defined spending date.
Sinking Fund Formula and Timing
The calculator converts APY into an effective weekly, biweekly, or monthly rate. The current balance compounds for each period, and the required contribution is added at period-end. When APY is 0%, the remaining amount after the current balance is divided evenly across the available contribution periods.
Required contribution = [target − current balance × (1 + periodic rate)periods] ÷ future-value annuity factor. Complete weekly or biweekly periods are used, so a date-based horizon may not equal a whole number of months.
If the current balance already meets the target, the required contribution is zero and the page shows an already-funded state. If the balance could reach the target through the entered APY alone, the required contribution can also be zero, but that result still depends on a constant-rate assumption.
Worked Example: Planned Annual Expense
For a $12,000 target, a $2,000 current balance, 10 months remaining, monthly contributions, and 0% APY, the funding gap is $10,000 and the required monthly contribution is $1,000. Total new contributions are $10,000 and modeled interest is $0.
Using the Result
Choose a frequency that matches how you move money, then compare the monthly equivalent with your cash flow. Total new contributions and estimated interest explain how the target is funded. Use the Savings Goal Calculator when the question is how long a fixed contribution may take, or the 50/30/20 Budget Examples to place the contribution within a broader monthly plan.
Common Mistakes and Limitations
Do not use an emergency reserve and a sinking fund as if the same cash were available for both goals. Avoid mixing weekly contributions with monthly assumptions, assuming APY is guaranteed, or forgetting that the target amount itself may change. The model excludes fees, tax, irregular deposits, early withdrawals, and currency conversion.
Frequently Asked Questions
Is a sinking fund the same as an emergency fund?
No. A sinking fund prepares for a known or recurring expense. An emergency fund is a general liquid buffer for unexpected essential costs or income disruption.
What happens when APY is zero?
The calculator uses simple division: the remaining target gap is spread across the available end-of-period contributions.
Can the goal label be shared or tracked?
No. The optional label is shown only in the current page UI. It is not added to URLs, canonical tags, structured data, or analytics events.
Why can the displayed contribution differ slightly from target divided by months?
Weekly and biweekly schedules use complete contribution periods, and positive APY adds modeled interest. Calculations use full precision before display rounding.