Runway

For a startup not yet making money, the most important number may be how long it has left before the cash runs out. That is its runway.

Runway is the length of time a company can continue operating before it runs out of cash, given its current cash reserves and rate of spending. For a startup burning through cash on the way to profitability or its next funding round, runway is the measure of how much time it has left, and managing it is among the most vital disciplines of survival.

Time before the cash runs out

Runway is calculated simply: the cash a company has, divided by its burn rate, the rate at which it is spending, gives the number of months it can survive before the reserves are exhausted. It is, in effect, the company's life expectancy at its current rate of spending, absent new revenue or funding. A startup with eighteen months of runway has a year and a half to reach a sustainable position or raise more money; one with two months is in crisis. Runway turns the abstract danger of running out of money into a concrete, countable measure of the time available.

Why it governs decisions

Runway governs a startup's decisions because it defines the time within which the venture must achieve what it needs to survive: reaching profitability, hitting the milestones that justify the next funding round, or proving the business works. A founder must reach those goals before the runway ends, which shapes priorities, the pace of spending, and when to start raising money, since raising takes time and cannot be left until the cash is nearly gone. Misjudging runway, believing there is more time than there is, leads to the fatal error of running out of money with the goal still out of reach.

Extending it

Because runway is survival, much of startup management is about extending it: raising more money to add to the reserves, or cutting the burn rate to make the existing cash last longer. When runway grows short, startups often cut costs sharply to extend it and buy time, even at the expense of growth, since survival comes first. The discipline is to monitor runway constantly, to act, by raising or cutting, well before it runs out, and never to let the cash dwindle to the point where the company has no time left to save itself. Running out of runway is, for most startups, simply the end.

Runway is the time a company has before its cash runs out, the measure, found by dividing reserves by burn rate, of how long it can survive at its current pace. It governs the decisions of any cash-burning venture, defining the window within which it must reach profitability or new funding, and its management, extending it by raising money or cutting costs and never miscalculating how much remains, is among the most fundamental disciplines of keeping a startup alive long enough to succeed.