Runway is an estimate of how long available cash can cover a monthly shortfall. It is only as useful as the assumptions inside it. Before making a major decision, compare several scenarios.
Start with the cash you can actually use
Exclude retirement funds, borrowing capacity, and money already needed for known bills. Decide what emergency reserve remains protected. Separate business operating cash from household cash so you do not count the same dollar twice.
Run three scenarios
Use the runway calculator for your current expected take-home, a lower-income case, and a zero-business-income case. Include reliable income that would remain in the household, but do not assume a pending sale will close.
As an illustrative example, $18,000 of spendable cash and a $2,000 monthly shortfall gives nine months. If the shortfall rises to $3,000, it becomes six months. These are arithmetic examples, not suggested reserve targets.
Look beyond averages
A monthly average can hide a large annual insurance payment, seasonality, a client paying late, or equipment replacement. Make a month-by-month cash calendar for uneven costs and collections.
Stress-test your largest customer leaving, a slower season, and an unexpected expense. The purpose is to identify the response you would need, not to predict every problem.
Choose a review trigger
Write a cash balance or date at which you will review the plan. Decide what steps happen before the reserve is exhausted. A fallback is more useful when you still have time to act.
Discuss the assumptions with your household and appropriate advisers. A calculator cannot decide whether a job change fits your personal situation.
Next step: write your base case, slow-sales case, and fallback in the decision workbook. Keep the plan current as your evidence changes.