Burn Rate vs Runway: What Every B2B SaaS Founder Needs to Know
Every investor you will ever speak to will ask you the same two questions within the first ten minutes: what is your burn rate, and how much runway do you have? These are not trick questions. They are the baseline of financial fluency that every early-stage founder needs to have at their fingertips.
And yet, in conversations with founders across the region, we regularly encounter confusion about what these numbers actually mean, how to calculate them correctly, and perhaps most importantly, what to do about them. This article will cover all three.
What is burn rate?
Burn rate is the rate at which your company is spending its cash reserves. It is typically measured monthly, and it comes in two forms: gross burn and net burn.
Gross burn
Gross burn is the total amount of cash your company spends each month before accounting for any revenue. If your salaries total $80,000 per month, your office costs $5,000, your software subscriptions run $3,000, and your marketing spend is
Gross burn tells you the absolute minimum amount of cash your business consumes to operate. It is useful for understanding your cost structure and for modelling what happens if revenue drops suddenly.
Net burn
Net burn is gross burn minus your monthly revenue. If your gross burn is
As you grow your revenue, your net burn should shrink even if your gross burn stays constant or increases slightly. The moment your MRR exceeds your gross burn, you are profitable on a cash basis.
Most founders know their gross burn. Fewer track their net burn monthly. The ones who do are always in a stronger position when it is time to raise.
What is runway?
Runway is the number of months your company can operate before running out of cash, calculated at your current net burn rate. The formula is simple:
Runway (months) = Cash in bank / Monthly net burn
If you have $600,000 in the bank and your net burn is $70,000 per month, your runway is approximately 8.6 months. This number should be reviewed every month and updated whenever your burn changes significantly, whether because of a new hire, a contract signing, or a shift in your revenue.
Why both numbers matter — and why they tell different stories
Burn rate and runway are related but they are not the same measure. Burn rate tells you the speed at which you are consuming cash. Runway tells you how much time you have. The key insight is that you can extend your runway in two ways: by reducing your burn rate (spending less) or by increasing your revenue (so your net burn shrinks).
Most early-stage founders instinctively try to extend runway by cutting costs. This can work, but it often slows growth in ways that make the next fundraise harder. The better question to ask is: which spend is contributing to revenue, and which is not? This is where the initiative-based approach to financial planning changes the conversation. Instead of asking 'what can we cut,' you ask 'which of our current initiatives has the best evidence of generating the expected return, and which do not?' Spend that is generating its expected outcome gets protected. Spend that has not met its expectation gets evaluated, adjusted, or cut.
What counts as a healthy runway?
The general rule in venture-backed startups globally is that you should always have at least twelve months of runway. Eighteen months is comfortable. Six months or less is an emergency.
Start your fundraise when you have at least 9 months of runway remaining. By the time you close, you will want to have used no more than 6 of them.
How to calculate your runway correctly
The most common mistake founders make is calculating runway using gross burn rather than net burn. If your gross burn is
The second most common mistake is using a static burn figure. Your burn rate is not constant. It will change as you hire, as you run campaigns, and as your revenue grows. A good runway calculation uses a three-month rolling average of net burn, updated monthly, rather than a single point-in-time figure.
The third mistake is failing to model what happens to your runway if things go slower than expected. Build a conservative scenario in which revenue growth is 20 to 30 percent slower than your base case and see when you run out of money. If the answer is uncomfortable, you need either to raise sooner or to find ways to slow burn without sacrificing the initiatives that are actually working.
The relationship between burn rate and your next fundraise
Investors do not just want to know your runway today. They want to know whether the capital they are about to give you will be enough to reach the milestones that justify the next round. This is sometimes called milestone-to-milestone fundraising. The question to answer before every raise is: what is the one or two things we need to prove with this capital that will make the next round fundable?
Model your burn against those milestones, not against a calendar date. Ask: at our current burn rate, when will we achieve this milestone? How many months of runway do we have beyond that point to run the next fundraise process? If the answer to the second question is less than six months, you are cutting it too close.
Practical steps to manage burn rate
- Set a monthly financial review. Block time at the start of every month to update your actuals: cash in bank, MRR, gross burn, net burn, runway. This should take no more than two hours if your books are in order.
- Track burn by initiative. Do not just know what you are spending. Know what you expected each spend to produce, and whether it did.
- Set a burn alert threshold. Decide in advance: if our runway drops below X months, we will take specific actions (begin fundraise, cut specific spend, accelerate revenue efforts). Having this decision made in advance prevents panic-driven choices.
- Share runway updates with your co-founders and key team members. Financial opacity within the leadership team leads to misaligned decisions about hiring, spending, and priorities.
Ready to apply this to your business? Get early access to YourCFO at yourcfo.tech.