Gross Burn vs Net Burn: Which One Sets Your Runway
By Devon Coombs, CPA, MBA · Teaching Professor of Finance, Santa Clara University · Reviewed August 2026
Compute stated runway on net burn, monthly cash out minus cash in, because runway measures how fast the bank balance is actually falling. Stress test on gross burn, total spend with no revenue credit, because it shows the survival floor if revenue stalls or churns away. Boards typically want both figures, since the gap between them is exactly the revenue the plan depends on.
| Gross burn | Net burn | |
|---|---|---|
| Definition | Total monthly cash outflows | Monthly cash outflows minus cash inflows |
| Question answered | How long cash lasts if revenue goes to zero | How fast the bank balance is actually falling |
| Runway math | Cash divided by gross burn gives the stress floor | Cash divided by net burn gives stated runway |
| Revenue sensitivity | None; revenue is ignored | Falls dollar for dollar as revenue grows |
| Primary use | Cost discipline and downside planning | Board reporting, fundraise timing, burn multiple |
| Failure mode | Overstates need when revenue is durable | Understates need when revenue is fragile |
When Gross burn is the right tool
Gross burn is the lens for cost discipline and downside planning. It answers how long the company survives if revenue goes to zero, which is the relevant question when revenue is concentrated in a few customers, early in its life, or exposed to churn. Investors evaluating young companies often anchor on gross burn, since early revenue tends to be the least durable line in the model.
When Net burn is the right tool
Net burn is the figure for stated runway, fundraise timing, and efficiency metrics such as the burn multiple, because it reflects the actual monthly change in cash. Runway equals cash on hand divided by monthly net burn, and 12 to 18 months of runway is generally treated as a healthy fundraising window. Net burn is only as reliable as the revenue inside it, so it belongs next to a view on revenue durability.
The common mistake
Founders compute runway off whichever burn figure flatters the story, most often a net burn built on revenue that has not yet proven durable. A company spending $400,000 a month against $250,000 of revenue reports $150,000 of net burn and a comfortable runway, yet if two anchor customers churn, burn snaps back toward the gross figure and runway can compress by more than half. The discipline is to publish runway on net burn while tracking the gross burn floor, and to time the raise against the floor rather than the flattering number.
Work the numbers yourself
Both concepts are taught in depth, with practice questions, in the free Entrepreneurial Finance course.