How much cash runway is enough for a small business?

Start with net burn, not just the bank balance

Cash runway is the number of months a business can keep operating before its available cash is exhausted. The useful version protects a safety buffer first, then divides the remaining cash by monthly net burn.

Net burn is monthly cash spending minus monthly cash income. If income already covers spending, a simple runway number is less useful; focus instead on cash-flow timing and the size of the reserve.

Use three scenarios

A single forecast can create false confidence. Compare a base case with a slower-sales case and a cost-reduction case. Change one assumption at a time so the result shows which risk matters most.

For example, a business with 50,000 of cash, a protected 10,000 buffer, 12,000 of monthly receipts and 18,000 of monthly payments has 40,000 of usable cash and 6,000 of net burn. The simple runway is about 6.7 months before one-off costs or timing differences.

• Base case: use the recent average for income and spending.
• Pressure case: reduce expected income and include known one-off costs.
• Action case: model costs you could realistically pause or remove.

Reconcile the inputs to cash timing

Use cleared bank balances for available cash and map receipts and payments to the month they are expected to clear. An unpaid customer invoice is not available cash, while VAT, payroll, loan repayments and annual renewals can leave the bank even when the profit forecast looks positive.

Protect the safety buffer before calculating runway. If the buffer would be used for a specific commitment such as payroll or tax, label it separately rather than quietly treating it as general operating cash.

Connect runway to an action ladder

Write actions against thresholds before the business reaches them. A first threshold might trigger weekly collections review and a pause on optional commitments. A lower threshold might trigger a funding discussion, supplier negotiation or a revised hiring plan. The exact levels depend on the business; the important control is deciding while options remain.

Update the calculation after a large receipt, tax payment, new recurring cost or material forecast change. Pair the runway number with the cash-flow forecast because a monthly average can hide a shortfall in the middle of the period.

Turn the answer into a trigger

Choose a runway threshold that prompts action before cash becomes urgent. The right buffer depends on revenue predictability, access to finance, customer concentration and how quickly costs can change.

This is planning guidance, not financial advice. Reconcile the inputs to current bank balances and your own cash-flow forecast before making a funding or spending decision.