Sinking Fund Calculator & Annual Bill Calendar

Plan for bills that do not arrive monthly

Monthly bills can vary, and less-frequent bills can be easy to miss in a monthly plan. List the obligations you actually pay, verify their dates and amounts, and compare them with the money available in your bill fund. This planner makes the timing visible so you can check for a shortfall before a due date.

What the planner does

You list each irregular bill — what it costs, how often it hits, and which month it falls due. The tool spreads every bill across the year, totals each month, and does three things: it draws a 12-month calendar so you can see the shape of your year, it flags your worst month (the one that spikes), and it works out a long-run average monthly amount to set aside. Whether that amount covers the next bill depends on when you start and how much is already in the fund. The funding check models those two inputs and reports any additional opening amount needed.

Two funding numbers: long-run contribution and opening balance

A useful long-run target for lumpy bills is simple: add up a full year's costs, divide by twelve, and move that slice into a separate account every month. It fully pre-funds the cycle only when you start far enough ahead or add an opening balance. The date-by-date check puts your monthly transfer and each bill on the calendar, then tracks the balance after every event. Choose which comes first when dates match. The lowest running balance determines the opening requirement; it can be larger than a calculation using month totals.

A worked example

Say you carry $600 car insurance billed twice a year (March and September), a$1,200 property-tax bill in April, $80 registration in July, and you set aside $500 for the holidays in December. That’s $2,980 a year. Spread evenly that’s about $248 a month — but your calendar shows the real story: April is your worst month at $1,200, with March and September close behind. Budget the $248 average and April still hurts. The start-month and current-balance fields calculate the opening catch-up needed for the modeled 12-month sequence.

Why the transfer day changes the answer

For a simpler example, enter a $600 annual bill due January 5, a $50 monthly transfer on day 20 and a zero starting balance. Before the first transfer, January 5 is $600 short. If the transfer is available on January 1, the opening requirement falls to $550. The annual total is identical. Only the order changes.

For the $2,980 example above, the default transfer is $248.34, rounded up from the exact monthly average. The downloadable ledger records each transfer and charge, so you can check the balance yourself. A smaller transfer can increase the required opening reserve; it does not make the bills cheaper.

Keep it locally — save, print, and export

Your list is saved in this browser, so you can come back and tweak it as bills change. When it’s right, you have several ways to take it with you: Print / Save as PDF gives you a printable calendar and funding ledger to pin up or file, Download calendar (.ics) drops an all-day reminder for each bill straight into Google Calendar, Apple Calendar or Outlook, and Download CSV exports every bill and month total and the date-by-date balance ledger ready for a spreadsheet. Bill names and amounts are deliberately not placed in a shareable URL; a financial plan in a URL can leak through browser history, copied links, recipients, or network logs.

What to put in it

Use these only as prompts, then verify the amount, frequency and due date from current documents:

• Insurance — auto, home or renters.
• Property tax — only if it is not already handled through escrow or another monthly plan.
• Vehicle registration / tags and any emissions or inspection fees.
• HOA or condo dues and assessments.
• Annual renewals — warranties, memberships, domains, software, professional licenses.
• Seasonal spikes — holidays, back-to-school, birthdays you can see coming.

Assumptions and limitations

• It plans, it doesn’t predict. The numbers are whatever you enter. A premium that rises or a surprise repair won’t be in here until you add it.
• Monthly cycles only. Frequencies are monthly, quarterly, twice-a-year, yearly and one-off. Use a separate weekly cash-flow plan for weekly charges; monthly averaging loses their timing.
• One monthly transfer, calendar dates. The plan starts on the first day of your chosen month and runs for 12 months. It does not adjust for weekends, bank holidays, pending transactions or weekly pay. Enter the day funds are available and verify actual processing times. A one-time bill occurs once at the next matching month in this planning cycle.
• No income or affordability test. It maps entered outflows and a reserve balance; it does not decide whether the modeled transfer fits the household's income and essential expenses.

Frequently asked questions