A founder who says "we have a year of runway" is usually citing a gut feeling, not a calculation. Runway is one of the few startup metrics with a precise, checkable formula — cash on hand divided by net monthly burn — but founders routinely miscount what belongs in "burn," which quietly shortens or inflates the real number. Here's how to calculate it correctly and how much of it you actually need.
What is startup runway, exactly?
Runway is the number of months a company can keep operating before its cash balance hits zero, assuming spending and revenue continue at current trends. It answers one question: how much time is left to hit the next milestone — profitability, a funding round, or a strategic sale — before the business runs out of money.
It is not the same as cash in the bank. A startup with $2 million in the bank and a $500,000 monthly burn has four months of runway, not "a lot of cash." Runway is a rate calculation, not a balance-sheet snapshot, which is why two companies with identical bank balances can have wildly different survival windows.
How do you actually calculate it?
The core formula, as TechCrunch's guidance on startup financial planning lays out, is straightforward: divide available cash by monthly expenses, then adjust for revenue coming in. In practice, that means four steps.
- Total your cash on hand. Use the actual bank and investment-account balance today, not a projected raise that hasn't closed.
- Calculate gross monthly burn. Add up everything spent in a typical month — payroll, rent, software, contractors, marketing, R&D.
- Subtract monthly revenue to get net burn. If the company brings in recurring revenue, net burn (gross burn minus revenue) is the number that determines survival time, not gross burn alone.
- Divide cash by net burn. The result is your runway in months. A company with $1 million in cash, $100,000 in monthly expenses, and $20,000 in monthly revenue has a net burn of $80,000 and roughly 12.5 months of runway.
That same TechCrunch guidance on building investor-ready financial models notes that credible projections stress-test this number under a zero-revenue scenario, not just the base case — because early revenue is the assumption most likely to slip.
How much runway should an early-stage startup keep?
TechCrunch's reporting on startup runway puts the working benchmark at 12 to 18 months for seed and Series A companies — enough time to reach real product-market signals and still leave a buffer for a slower-than-hoped fundraising cycle. Less than six months of runway typically forces a company into reactive decisions: emergency cost cuts, a rushed bridge round, or a fire-sale acquisition, none of which happen on the founder's terms.
The right number isn't fixed, though. It depends on how long the company's fundraising or sales cycle actually takes to close, and on how much operating leverage the business has once it starts generating revenue. A startup selling to enterprise customers with nine-month sales cycles needs more cushion than one with self-serve signups and fast payback.
What should — and shouldn't — count as monthly burn?
Burn rate calculations go wrong most often by omission. A complete monthly burn figure includes salaries and benefits, contractor and vendor payments, office and infrastructure overhead, marketing spend, and R&D costs — the full operating base, not just the obvious payroll line. It should also reflect known one-time costs spread across the months they'll actually hit, like annual software renewals or a planned hiring wave.
What it shouldn't include is money that hasn't landed: a verbally committed investment, a grant still in review, or a customer contract still being negotiated. How a company books that activity also matters — the accounting method it uses changes how visible actual cash movement is in the books, as the U.S. Small Business Administration's guidance on managing business finances notes when comparing cash-basis and accrual accounting. A founder tracking runway off accrual-basis statements without adjusting for cash timing can easily overstate how much runway is actually left.
How can founders extend runway without breaking the company?
The two levers are spending less and earning sooner, and the disciplined version of "spend less" is measuring capital efficiency — roughly a dollar of return for every dollar spent on growth — before adding more spend rather than after. That means testing whether a marketing channel or a new hire actually shortens the path to revenue before scaling it, not cutting broadly and hoping.
On the revenue side, even modest recurring income changes the math directly, since it reduces net burn dollar for dollar in the runway formula above. A startup that converts $10,000 of monthly gross burn into $10,000 of monthly revenue effectively buys itself extra months without touching the bank balance at all.
For a related startups perspective, read Celebrating 30 Years of Excellence: MILO Range's Journey.
For more context, read Celebrating 30 Years of Excellence: MILO Range's Journey.
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