Runway is the number of months a startup can keep operating before it runs out of cash, calculated by dividing current cash on hand by monthly burn rate. It’s one of the simplest numbers in startup finance, and one of the most important to track constantly.
How runway is actually calculated
The formula is straightforward: take your total cash reserves and divide it by your net monthly burn rate, meaning how much cash the company spends each month after accounting for any revenue coming in. If a company has $600,000 in the bank and burns $50,000 a month after revenue, it has 12 months of runway.
How much runway is considered safe
Most startup advisors and investors suggest maintaining at least 12 to 18 months of runway at any given time, treating anything below 6 months as a genuine red flag that requires immediate action, either cutting costs or raising money urgently. The reasoning is straightforward: fundraising itself takes months, so a founder who waits until they have only 2 or 3 months of runway left is negotiating from a position of real weakness.
Why runway shrinks faster than founders expect
Burn rate tends to increase as a company hires more people, and revenue growth is rarely as fast or as linear as founders initially project. Recalculating runway monthly, rather than assuming last quarter’s numbers still hold, is a basic discipline that prevents nasty surprises.
Frequently asked questions
How do you calculate startup runway?
Divide current cash on hand by your net monthly burn rate (monthly spending minus monthly revenue).
What counts as dangerously low runway?
Most advisors consider under 6 months a serious warning sign that requires immediate fundraising or cost-cutting action.
Does revenue affect runway calculations?
Yes, runway should be based on net burn, which accounts for incoming revenue, not just gross spending.
For more startup fundamentals, see Talmyn’s Business & Economics desk.
