Runway is the number of months a company can continue to operate before it runs out of cash. It is calculated by dividing the current cash balance by the monthly net burn rate. A company with $3M in the bank and a net burn of $200,000 per month has 15 months of runway. That number is the clock ticking in the background of every decision the company makes, from hiring to product development to fundraising timing.
The concept is simple, but managing runway well is one of the things that separates companies that survive from companies that do not. The fundamental mistake founders make is treating runway as a static number. It is not. Burn rate changes every month. A new hire increases burn. Landing a large customer decreases net burn. An unexpected legal expense or infrastructure cost spikes burn in a single month. Runway should be recalculated at least monthly, and the recalculation should account for committed future expenses (signed contracts, upcoming payroll increases, annual renewals) rather than assuming current burn holds steady.
The relationship between runway and fundraising is the most consequential application of this metric. Fundraising takes time. A Series A process, from the first partner meeting to wire in the bank, typically takes 3 to 6 months. If you start fundraising with only 6 months of runway, you are negotiating from a position of visible desperation. Investors know your timeline. They can wait you out. Your term sheet options narrow because only investors willing to fund a company with limited leverage will engage. The standard guidance is to begin fundraising when you have 9 to 12 months of runway remaining, which means your post-raise runway of 18 to 24 months starts shrinking the day the money hits the account.
The appropriate amount of runway varies by stage and context. Pre-seed and seed-stage companies typically target 18 to 24 months of runway per round. This provides enough time to build an initial product, find early customers, and demonstrate enough traction to raise a Series A. Series A companies may target similar timeframes but with higher absolute burn, reflecting the need to invest in go-to-market and team scaling. At later stages, the math shifts because companies may be closer to profitability and can extend runway by modulating growth spending.
The concept of “default alive” versus “default dead,” coined by Paul Graham, reframes runway as a strategic question. A default-alive company is one that, at its current revenue growth rate and expense level, will reach profitability before cash runs out. A default-dead company will run out of money first. This binary framing is useful because it forces founders to decide whether they are building a company that requires continuous external capital or one that can survive independently. Many companies oscillate between these states as they add headcount, invest in growth, or face revenue setbacks.
For angel investors and early-stage VCs, runway is a screening metric. An investor evaluating a seed deal will mentally calculate how much runway the round provides and whether that is sufficient to reach the milestones that would justify a Series A. If the math does not work, the deal does not work, regardless of how compelling the product or team might be. Founders who demonstrate a clear understanding of their runway, a realistic burn plan, and a set of achievable milestones within that runway are significantly more fundable than those who present ambitious plans without connecting them to the cash reality.
Frequently Asked Questions
How do you calculate runway?
Runway equals current cash balance divided by monthly net burn rate. If you have $1.8M in the bank and your net burn is $150,000 per month, your runway is 12 months. Use net burn (total expenses minus revenue) rather than gross burn for an accurate calculation. Update the calculation monthly because both your cash balance and burn rate change over time.
How much runway should a startup have after raising?
The standard benchmark is 18 to 24 months of runway after closing a funding round. This provides enough time to hit the milestones required for the next round while leaving a buffer for fundraising itself (which takes 3 to 6 months). Raising less than 12 months of runway puts you in a position where you need to start fundraising almost immediately after closing, which is a sign the round was undersized.
What is the difference between default alive and default dead?
A concept popularized by Paul Graham. A startup is 'default alive' if its current revenue growth rate and expense trajectory will make it profitable before it runs out of cash. A startup is 'default dead' if it will run out of cash before reaching profitability at current trends. This framing forces founders to confront whether they need external capital to survive or whether they could, in a worst case, tighten spending and reach breakeven.
