What it means
A business that spends more than it takes in is drawing down a finite pool of cash, and runway is how long the pool lasts. The arithmetic is simple: $3 million in the bank and a net outflow of $250,000 a month is twelve months.
The management of it is not, because the burn rate changes with hiring and revenue, the cash balance changes with receipts and one-off payments, and the options for extending runway (cutting costs, raising money, growing revenue) each take time to execute. Runway must be calculated on the forecast, not the current month.
A company that is about to hire ten people will burn faster next quarter than this one; a company whose revenue is growing will burn slower. The proper calculation runs the monthly cash forecast forward, month by month, with planned hiring, expected revenue growth, known one-off payments (a tax bill, a lease deposit, a debt repayment) and seasonal effects, and reads off the month in which cash reaches zero, or a minimum balance below which the business cannot safely operate.
The result is often shorter than the simple division suggests, because burn usually rises before it falls. The uses of runway are strategic.
It sets the fundraising timetable: with a six-month raise process, a company must begin at least nine months before the cash ends, and ideally at a point when its metrics are strong rather than when it is desperate. It sets the milestone plan: what must the business achieve (product launch, revenue level, customer count) within the runway to justify the next round or reach break-even.
It frames the spending decisions: every hire and every campaign is a reduction in runway, to be weighed against the progress it buys. And it defines the contingency: what cuts would extend runway by how much if the plan slips or the market turns.
Extending runway has three levers with different speeds. Cutting costs is fastest: headcount reductions, contract cancellations, and deferred spending can extend runway within a month or two, though at the cost of progress and morale.
Growing revenue is slower but more valuable, since it reduces burn while building the business. Raising capital takes longest and depends on the market and the company's story.
Companies in trouble often discover that the third lever is unavailable and the second is too slow, leaving only the first, applied late and hard. Investors read runway as a measure of management discipline.
A company that knows its runway to the month, has a forecast behind it, and has a plan for the milestones within it is fundable; one that cannot answer the question, or answers it with a number that ignores its own hiring plan, is not. The related measures, burn rate and burn multiple, complete the picture: runway says how long the cash lasts, burn multiple says whether it is buying efficient growth.
In practice
Real-world examples.
Example
A software start-up with $2 million and net burn of $100,000 a month reports twenty months of runway and plans to reach cash break-even before it needs to raise again.
Example
A retailer in a downturn calculates its runway at seven months on current losses and cuts store hours and stock purchases to extend it to fourteen.
Example
A biotech company reports thirty months of runway after a raise, enough to reach two clinical readouts that will determine its value.
Think of it
“Cash runway is how far you can travel before running out of fuel-measured in months of operation.
Formula
Calculation
Cash Runway (months) = Cash balance / Net monthly burn rate
Net Burn Rate = Monthly cash outflows minus Monthly cash inflows
Forecast Runway = The month in which the forecast cash balance falls below the minimum operating balance, from a month-by-month forecast
Runway extension from a cost cut = Cash balance / (Burn rate minus Cut) minus Cash balance / Burn rate
Worked example. A medical device start-up has $5,400,000 in the bank. Current monthly figures: salaries $380,000; clinical trial costs $120,000; other operating costs $90,000; total outflow $590,000; revenue from early sales $60,000; net burn $530,000.
Simple runway = $5,400,000 / $530,000 = 10.2 months.
Forecast runway: the plan adds four engineers in months 2 to 4 (raising salaries to $440,000 by month 4), a trial expansion in months 5 to 9 (trial costs $180,000 a month), a $200,000 regulatory filing fee in month 7, and revenue growing to $110,000 a month by month 12. Running the forecast:
- Months 1 to 3: net burn about $530,000, $560,000, $590,000; cash at end of month 3 about $3,720,000
- Months 4 to 6: net burn about $600,000, $650,000, $650,000; cash at end of month 6 about $1,820,000
- Month 7: net burn $650,000 plus $200,000 filing fee; cash $970,000
- Month 8: net burn about $640,000; cash $330,000
- Month 9: net burn about $630,000; cash below zero
Forecast runway is about 8.5 months, not 10.2, because the plan raises burn before revenue catches up. Against a minimum operating balance of $300,000 (one month of payroll as a floor), the runway is 8 months.
Fundraising implication: a Series B is expected to take five to six months. Starting at month 2 leaves the company negotiating in months 5 to 7 with three to five months of runway visible to investors: weak. The board decides on two actions. First, defer two of the four hires and the trial expansion by three months, which reduces cumulative burn over nine months by about $700,000 and extends forecast runway to about 10 months. Second, arrange a $1,500,000 venture debt facility, drawable at the company's option, which extends the outside runway to about 13 months and lets the raise begin from a position of strength at month 3 with ten months of cover.
Contingency plan, documented for the board: if the raise has not closed by month 8, a cost reduction of $200,000 a month (a hiring freeze, trial pause and 15% headcount cut) would extend the remaining runway from about 3 months to about 6, and the venture debt would be drawn. The chief executive's monthly report shows cash, net burn, forecast runway on the plan, and runway under the contingency.Case study
Seen in the real world.
A consumer subscription start-up raised $8,000,000 and, with strong early growth, hired quickly. Its finance lead reported the cash balance monthly but not the runway, and the board, focused on subscriber growth, did not ask. Fourteen months later, when the chief executive began preparing the next round, the finance lead calculated runway for the first time: $2,100,000 at a net burn of $620,000, less than four months, with a $300,000 annual software contract renewal due in the next month.
The round could not be closed in time. The company cut 40% of its staff, paused all marketing, negotiated a three-month deferral of the software contract, and took a bridge loan from its existing investors at terms that gave them a substantial discount on the next round. The round closed five months later at a valuation 30% below the previous one.
The new lead investor's first requirement was a monthly runway report with the forecast behind it and a board rule that any hiring plan be presented with its runway effect. The chief executive's retrospective, circulated to other founders, said that the company had tracked every metric except the one that determined whether it would exist, and that the cost of not tracking it had been a third of the team and a third of the valuation.
Watch out
Common mistakes.
- Calculating runway from the current month's burn when the plan will raise burn. Use the forecast, month by month, including hiring and one-off payments.
- Starting a fundraise with less than nine months of runway, which means negotiating from weakness and risks failing to close in time.
- Reporting cash without runway, so that the board sees a balance and not a deadline.
Questions
People also ask.
How much runway should a start-up have?
Eighteen to twenty-four months after a raise is the usual target; begin the next raise with at least nine months left. In difficult funding markets, more.
Does runway apply to profitable companies?
Only when they are consuming cash: in a loss-making investment phase, a downturn, or a turnaround. The same arithmetic then applies.
What extends runway fastest?
Cost cuts, especially headcount, within a month or two. Revenue growth is slower but better. Capital raising takes longest and is least certain. A contingency plan should specify the cuts and their effect in advance.
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