What Is Runway and Burn Rate for Fundraising?
Runway and burn rate determine how long your company can survive on current cash. Learn how investors use these metrics and how to manage them strategically.
Key Takeaways
- Runway = current cash divided by monthly net burn rate
- Start fundraising with at least 6-9 months of runway remaining
- Raising from a position of desperation produces bad terms — raise from strength
- Extending runway by reducing burn buys optionality and negotiating leverage
Runway and burn in a fundraising context
Burn rate is how much net cash your company spends per month (total cash out minus total cash in). Runway is how many months of cash remain at the current burn rate. These metrics tell investors how urgently you need their money — which directly affects your negotiating leverage. A company with 18 months of runway can walk away from a bad deal. A company with 6 weeks of runway cannot.
When to start fundraising
The cardinal rule of fundraising timing is: start with enough runway that you can afford the process to take longer than expected, because it always does. Fundraising for a seed round typically takes 3-6 months from first outreach to money in the bank. Series A typically takes 4-9 months. Start when you have 6-9 months of runway remaining minimum — 12 months is better. Founders who wait until they have 3-4 months of cash left are forced into a desperate fundraise that produces either bad terms or no deal.
Milestones and the next round
Investors think about burn rate in relation to the milestones the investment is meant to fund. The question they are asking is: given what they are raising and at what burn rate, will this company reach the next fundable milestone before the money runs out? If a company is raising £800,000 at a £100,000 monthly burn, they have 8 months — which may not be enough to prove the next round's key metrics. Investors will probe this and may ask you to reduce burn, raise more, or show a credible path to reaching milestones within the runway.
Extending runway without raising
Before fundraising, review your burn rate critically. Every pound of monthly burn you can eliminate without harming growth extends your runway and improves your negotiating position. Common burn reduction levers: delay non-critical hires, renegotiate supplier contracts, move to lower-cost office space or fully remote, cut software subscriptions that are not actively used, and focus marketing spend on the highest-ROI channels only. A company that reduced burn from £120,000 to £80,000 per month extended an 8-month runway to 12 months without raising a penny.
Default alive or default dead
Paul Graham's concept of default alive vs default dead captures the strategic importance of burn management. A company is default alive if, at current growth rates and burn, it will become profitable before running out of money. It is default dead if the current trajectory leads to cash exhaustion before profitability. Default alive companies have options — they can choose to raise on their own terms or choose not to raise. Default dead companies must raise or die. Always know which side of this line you are on.