Runway is a liquidity measure, not an accounting-profit measure. A company can show positive revenue while using cash to pay overdue supplier invoices, build inventory or wait for customers to settle. Start with money available for ordinary operations, remove restricted balances and funds already owed as taxes or payroll deductions, and be explicit about the date of the balance. This gives the estimate a usable starting point rather than a reassuring but misleading bank total.
Formula and definitions
Formula: Runway in months = usable cash ÷ average monthly net cash burn
Define usable operating cash
Count cash that management can actually use for rent, payroll, suppliers and ordinary operations. Do not count a tax reserve, client trust balance, restricted grant or credit facility as though it were cash in the bank. If the bank balance includes money already committed to next week's payroll, subtract that obligation before applying the formula. State the measurement date and repeat the calculation from reconciled accounts rather than a remembered balance.
Measure net burn from cash movements
Net burn is cash paid out minus cash collected over a representative period. It is different from a book loss because depreciation, unpaid invoices, inventory movements and financing can move cash without matching the income statement. Use at least several months when the business is seasonal, and separate a one-time equipment purchase or legal settlement from ordinary monthly operating costs. If collections are delayed, actual cash history is often a better warning than optimistic invoice dates.
Use scenarios instead of one confident answer
Calculate a base case, a slower-collections case and a cost-pressure case. In the downside version, delay uncertain receipts and include known renewals, taxes, seasonal payroll and supplier deposits. Averages are useful when conditions are stable, but they can hide a sharp cash trough around a single due date. Runway should be paired with the lowest projected weekly balance, because a business can hit a payment problem before an average-month calculation suggests the cash is gone.
Choose a decision threshold in advance
A practical warning threshold might be the cash needed to cover the next payroll cycle plus unavoidable bills, but each business should document its own minimum. Decide in advance which actions start at each level: freeze optional purchases, collect overdue invoices, shorten supplier commitments or speak with a lender. An alert is more useful when it leads to a defined action than when it is simply displayed on a dashboard.
Worked example
A company has $96,000 of unrestricted cash. Recent months show $18,000 of operating payments and $12,000 of collections, leaving $6,000 net monthly burn. The simple estimate is 16 months. If collections fall to $8,000 while monthly outflows rise to $20,000, burn becomes $12,000 and estimated runway drops to 8 months. That change justifies revisiting hiring and discretionary spending even though the opening bank balance has not changed.
| Item | Calculation or value | Meaning | |
|---|---|---|---|
| Base case | $96,000 | $6,000 | 16 months |
| Slower collections | $96,000 | $9,000 | 10.7 months |
| Higher cost pressure | $96,000 | $12,000 | 8 months |
Common mistakes
Do not treat a committed credit line as cash unless it is drawable and conditions are understood. Do not annualize one unusually good month without testing seasonality. Do not divide cash by gross expenses and call that runway when dependable collections continue. Record assumptions next to the estimate so another person can reproduce and challenge it.
Next steps
Update runway after a meaningful change in cash, collections, payroll or supplier terms. Pair the monthly estimate with a weekly cash forecast, an overdue-invoice list and a schedule of unavoidable payments. A forecast does not guarantee that a customer will pay on time; it makes the consequences of a delay visible while there is still room to react.
Frequently asked questions
What if monthly burn is negative?
If operating cash receipts consistently exceed cash payments, the business is not burning cash during that period; still model investment purchases, debt payments and seasonality before claiming unlimited runway.
Should financing be included?
Show operating runway separately from cash after confirmed financing, and label conditional credit separately so the base case does not depend on funding that may never arrive.
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