What Is Runway?
Runway measures how long a cash-consuming company can survive at its current spending pace. The metaphor comes from aviation: a startup needs to reach takeoff, meaning profitability or a new financing, before the runway ends. Because most venture-backed companies deliberately spend more than they earn to grow quickly, runway is the number that boards, founders, and investors watch most closely.
Runway is a dynamic figure rather than a fixed one. Hiring accelerates burn and shortens runway, while revenue growth, cost cuts, or new funding extend it. A company with strong gross margins and improving unit economics may see its runway lengthen every quarter even without raising, while a company scaling headcount ahead of revenue can watch two years of runway compress into one.
How to Calculate Runway
The formula is runway in months equals cash balance divided by monthly net burn, where net burn is cash spent minus cash collected. A startup holding $6 million with a net burn of $300,000 per month has 20 months of runway. If burn is uneven, most operators use an average of the last three months or a forward forecast rather than a single month's figure.
The calculation should reflect reality, not hope. Prudent CFOs model runway under a base case and a downside case where revenue grows slower than plan, and they exclude uncommitted funding sources. Timing also matters because a fundraise typically takes three to six months from first pitch to money in the bank, so founders are generally advised to start raising with at least six to nine months of runway remaining.
Why Runway Matters
Runway determines negotiating leverage. A startup raising with 18 months of cash can walk away from a bad term sheet, while one with three months left must accept whatever terms are offered, often a down round or a structured bridge. This is why standard advice is to raise enough for 18 to 24 months, giving the team time to hit milestones before facing investors again.
For candidates interviewing in venture capital, growth equity, or startup finance roles, runway questions test practical fluency. You may be asked to compute runway from a simple cash forecast, to explain how a hiring plan changes it, or to judge whether a company should extend runway with venture debt. The metric connects a startup's income statement ambitions to its balance sheet constraints.
