About the 13-Week Cash Flow Forecast
A 13-week cash flow forecast is the standard short-term tool lenders, turnaround advisers and finance teams use to see whether a business can pay its bills over the next quarter. Unlike a profit forecast, it tracks only cash actually received and paid, week by week, so it shows timing problems — a payroll week that lands before customer payments arrive — that monthly budgets hide.
This calculator builds the forecast from a few drivers: opening cash, typical weekly customer receipts with an optional growth rate, weekly operating payments, payroll on a weekly, every-two-weeks or monthly cycle, and monthly fixed costs such as rent and loan payments. Add one-off items — a tax payment, an equipment purchase, a customer deposit, a loan drawdown — on their own lines with the week they fall in.
The result shows the ending cash for each week, the lowest balance and when it occurs, and any weeks that dip below zero or below the minimum cash buffer you want to hold. Monthly items are placed in weeks 1, 6 and 10, the first week of each roughly 4.33-week month. Replace the driver amounts with your own figures from bank statements and receivables ageing for the most accurate view.
With the default inputs, the cash at end of week 13 is $82,889.61. Change any value above to recalculate instantly.
How to use the 13-week cash flow forecast
- 1Enter the cash in the bank at the start of week 1.
- 2Enter typical weekly customer receipts and any expected weekly growth or decline.
- 3Enter weekly operating payments, your payroll amount and schedule, and monthly fixed costs.
- 4List one-off receipts and payments with the week they occur, one per line.
- 5Set the minimum cash you want to hold, then review the low point and any shortfall weeks.
- 6Update the forecast every week, rolling it forward as actual figures come in.
Formula and method
The forecast is a running cash balance. Each week starts with the previous week’s ending cash, adds cash received from customers and any one-off inflows, and subtracts weekly operating payments, payroll in pay weeks, monthly fixed payments in weeks 1, 6 and 10, and any one-off outflows. Customer receipts begin at the weekly amount you enter and change by the weekly growth rate, compounded.
Every-two-weeks payroll falls in the first payroll week you choose and every second week after; weekly payroll falls in every week from that week on. The lowest balance, the first week below the minimum buffer and the count of negative weeks highlight when you may need financing. This is a direct (receipts and disbursements) cash forecast, so it ignores non-cash items such as depreciation.
- R
- Customer receipts in week 1
- g
- Weekly growth rate of receipts
- w
- Week number, 1 to 13
Worked examples
Service business with a tax payment in week 6
Receipts start at $40,000 a week and grow 0.5% weekly, totalling about $550,890 including the $15,000 deposit. Six biweekly payrolls ($180,000), 13 weeks of operating costs ($234,000), three fixed payments ($36,000) and $33,000 of one-off outflows total $483,000. Cash ends near $82,890, but it dips under the $20,000 buffer in week 2 (the first payroll) and again in week 6, when payroll, rent and the $25,000 tax bill land together and leave just $11,020.
Flat sales, weekly payroll, no one-offs
Each week brings in $25,000 and pays out $21,000 in operating costs and payroll, adding $4,000 — except weeks 1, 6 and 10, when $6,000 of fixed payments turn it into a $2,000 loss. Over 13 weeks cash grows by 10 × $4,000 − 3 × $2,000 = $34,000, from $30,000 to $64,000, and the low point is $28,000 after week 1.
Frequently asked questions
What is a 13-week cash flow forecast?+
It is a week-by-week projection of cash receipts and payments for the next quarter. Banks, lenders and turnaround advisers rely on it because it shows exactly when cash may run short, which a monthly profit-and-loss forecast cannot.
Why 13 weeks?+
Thirteen weeks is one quarter, long enough to cover a full cycle of payroll, rent, supplier terms and quarterly taxes, yet short enough that receipts and payments can be forecast with reasonable accuracy from invoices and contracts already known.
How is a cash flow forecast different from a profit forecast?+
Profit counts revenue when it is earned and costs when they are incurred. A cash forecast counts money only when it actually arrives or leaves the bank, so a profitable business can still run out of cash if customers pay slowly.
How much minimum cash should a business keep?+
A common rule of thumb is enough to cover at least one payroll plus a month of fixed costs, or two to four weeks of total payments. Businesses with lumpy receipts or seasonal sales usually hold more.
What should I do if the forecast shows a shortfall?+
Act early: collect overdue receivables, offer early-payment discounts, negotiate longer terms with suppliers, delay discretionary purchases, or arrange a line of credit before the weak week arrives. Lenders respond better to a plan than to an emergency.
Results are estimates for educational purposes and are not financial advice. Rates, fees and terms vary — confirm with your lender or a licensed advisor before making decisions.