Sinking fund planner

Sinking funds turn lumpy expenses into calm monthly math

Most budgets fail because they treat predictable expenses like surprises. Insurance premiums, tax payments, repairs, annual subscriptions, holidays, and travel do not happen every month, but they are not random.

The core formula

The calculator solves the future-value formula backward:

target = current x (1 + r)^months + payment x (((1 + r)^months - 1) / r)

That lets it find the monthly transfer that reaches the target by the deadline, after accounting for the current balance and savings yield.

How to use the answer

• Use the monthly transfer for automated budgeting.
• Use the biweekly transfer if you budget from paychecks.
• Use the weekly transfer if small frequent moves are easier to keep.

What belongs in a sinking fund

Good candidates are known, time-bound expenses: property tax, insurance premiums, quarterly taxes, home repairs, car maintenance, annual software, travel, or a planned purchase.

Emergency funds are different. Keep them separate so a planned vacation does not quietly eat the money meant for job loss or a serious repair.

Where to keep the money

Use a high-yield savings account, money-market fund, Treasury bill ladder, or another cash-like place when the deadline is close. A sinking fund is about certainty. Chasing a little extra return is not worth missing the date because the market moved against you.