Runway

Runway is the most sobering metric in startup finance: how many months you have before the money runs out. The formula is simple: Runway = Cash Balance / Monthly Net Burn Rate. If you have $750,000 in the bank and your net burn is $50,000/month, you have 15 months of runway.

Runway is a moving target that changes with every dollar you spend or earn. Revenue growth extends your runway; new hires shrink it. Smart founders maintain a dynamic model that recalculates runway based on actual monthly financials rather than relying on the number from their last board deck. Some companies calculate "default alive" vs. "default dead" — if your revenue growth rate continues, will you reach profitability before running out of cash? If yes, you're default alive. If no, you need to either raise more money or cut costs.

The general rule of thumb is to start your next fundraise when you have 6-9 months of runway remaining. Fundraising typically takes 3-6 months (sometimes longer), and you never want to negotiate from a position of desperation. Running out of runway is the number one killer of startups — not competition, not bad products, not failed marketing. Simply running out of cash.

Runway determines your strategic options. With 18+ months of runway, you can take risks, experiment, and be patient with fundraising. With 6 months, every decision is constrained by survival. With 3 months, you're in crisis mode — likely forced to accept bad terms, do emergency layoffs, or shut down. Understanding your runway and actively managing it is probably the single most important financial discipline for a startup founder. Every spending decision should be evaluated partly through the lens of its impact on runway.