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About this tool
Work out the monthly reserve for known irregular bills like insurance, servicing, fees and travel.
A sinking fund converts a lumpy bill you can see coming — an insurance renewal, a school term, a service, a holiday — into a level monthly reserve. This calculator returns two separate figures for each expense: the catch-up deposit, which is the sinking-fund annuity payment that closes the gap before the next due date, and the steady-state deposit, which is the amount per month once you have a full cycle to rebuild the fund. Confusing the two is why budgets break in renewal month.
Open Sinking Fund Calculator on AltFTool — it loads instantly in your browser.
Add each irregular bill with its Expense name, 'How often it repeats' (One-off up to Every 5 years), Amount due (₹), Months until due and Already reserved (₹) — press 'Add an expense' for more rows.
Enter your Monthly take-home income (₹) and optionally a 'Return on the reserve (% per year)'; the calculator warns when the combined reserves cross 25% of take-home.
Read 'Set aside each month' — the catch-up rate until approaching bills are funded — beside the smaller steady-state figure, review the 'Every fund, soonest first' table, then press Copy plan.
The bill due in four months needs a much bigger monthly deposit than its annual cost implies.
Several funds are summed into a single transfer you can automate.
Known bills stop being emergencies, so the contingency fund stays intact for real ones.
Divide what you still need by the number of months until the due date. For an ₹18,000 insurance renewal four months away with ₹3,000 already set aside, the shortfall is ₹15,000 and the monthly deposit is ₹3,750. Once that bill is paid, the ongoing cost is only ₹1,500 a month because you then have twelve months to rebuild it.
A sinking fund is for expenses you already know about — dates and amounts are predictable, so you save toward them deliberately. An emergency fund covers what you cannot predict, such as a job loss or a hospitalisation, and should not be drained by a bill you could see coming.
Anything large that arrives less often than monthly: insurance premiums, school and college fees, vehicle servicing and tyres, annual subscriptions, property tax and society maintenance, festival spending, travel, and appliance replacement. If it has broken your budget once, it needs a fund.
Somewhere separate from your spending account but reachable on the due date without a penalty — a second savings account, a sweep-in deposit, or a recurring deposit that matures before the bill. Avoid equity for money you will spend within a year or two. Informational only, not financial advice.
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