What it means
Every business that spends more than it collects is living on a clock, and runway tells you how much time is left on it. The calculation is deliberately blunt: take the cash you actually hold, divide by the net cash you lose in a typical month, and the answer is a number of months.
It is not a forecast of the future so much as a measure of how much room you have to change the future. Runway matters because almost every important decision in a growing company depends on it.
Hiring three engineers, signing a three year office lease or launching in a new country all shorten runway, and the honest question is whether the return arrives before the cash runs out. Investors ask about runway first because it tells them how urgently the company needs money and therefore how much bargaining power it has.
The number that drives runway is net burn, not gross spending. A business spending $500,000 a month while collecting $300,000 in customer receipts is burning $200,000 net, so growing revenue extends runway just as effectively as cutting costs.
This is why the metric is usually paired with burn rate rather than quoted alone. Two refinements make runway far more useful.
The first is using a rolling three month average burn instead of a single month, which smooths out one off items such as an annual insurance premium. The second is separating committed spending from discretionary spending, so you know how much runway you could recover in a hurry if a funding round slipped.
A common convention is that a company should start raising money when it has roughly nine to twelve months of runway left, because raising takes time and negotiating from a position of desperation is expensive. Runway below six months tends to change investor behaviour, and below three months it changes supplier and employee behaviour too.
In practice
Real-world examples.
Example
A direct to consumer skincare brand holds $900,000 in cash and burns $75,000 a month after allowing for subscription revenue. Its runway is 12 months, so the board agrees to open conversations with investors at the six month mark rather than waiting for the balance to look alarming.
Example
A logistics startup wins a contract that adds $80,000 a month in collections against a previous net burn of $120,000. Burn drops to $40,000 and runway on its $960,000 cash balance stretches from 8 months to 24 months, which removes the need for an emergency funding round.
Example
A biotech firm with $6,000,000 in cash and a $500,000 monthly burn has 12 months of runway, but a clinical trial milestone sits 14 months away. The chief executive delays two senior hires and renegotiates a laboratory lease to push runway past the milestone date.
Think of it
“Runway is how long your money will last-the time before you run out of fuel.
Formula
Calculation
Runway (months) = cash and cash equivalents / average net monthly burn
Net monthly burn = average monthly cash out - average monthly cash in
A software company holds $2,400,000 in the bank. It collects $150,000 a month from customers and spends $350,000 a month on salaries, hosting and marketing, so its net monthly burn is $350,000 - $150,000 = $200,000.
Runway = $2,400,000 / $200,000 = 12 months.
Now suppose the founders cut monthly spending to $300,000 while holding collections steady at $150,000. Net burn falls to $150,000 and runway becomes $2,400,000 / $150,000 = 16 months, so a 14% cut in spending bought four extra months of time.Case study
Seen in the real world.
This is an illustrative and entirely fictional scenario. Harborline Analytics, an invented data tools company, had raised $4,000,000 and was spending $400,000 a month while collecting $150,000, giving a net burn of $250,000 and 16 months of runway. The founders described the position internally as comfortable and approved a plan to double the sales team.
Six months later, cash stood at $2,500,000 and net burn had risen to $340,000 because the new salespeople had not yet closed anything, leaving roughly 7 months of runway. The board only spotted the change because a new finance lead started reporting runway monthly rather than quoting the original 16 month figure from the funding round.
In this fictional example the company paused hiring, moved two contractors onto part time terms and pushed collections from 60 days to 35 days, which lifted runway back above 11 months. That was enough time to run a proper funding process instead of accepting the first term sheet offered.
Watch out
Common mistakes.
- Dividing cash by gross monthly spending rather than net burn, which understates runway for any business with real revenue coming in.
- Quoting the runway figure calculated at the last funding round months after the fact, when spending and collections have both moved.
- Counting money that is committed but not yet received, such as an unsigned investment or an unpaid invoice, as though it were cash in the bank.
Questions
People also ask.
Does runway assume revenue stays flat?
The basic calculation does, which is why fast growing businesses usually also model a version where collections rise and compare the two.
Should restricted cash be included in the runway calculation?
No, because money held as a deposit or security against a lease cannot be spent on salaries, so it should be excluded from the cash figure.
How does a profitable company use runway?
It rarely needs the monthly version, but it still tracks the equivalent when funding a large project or an acquisition from its own cash reserves.
From the founder's library
Take it further with the book.
Build your financial confidence beyond this definition. Shihan's full-length guide, Accounting Fundamentals, takes the same plain-English approach and turns it into a complete, practical playbook for non-finance managers, business owners and students - with chapter-end quiz answers and presentation slides included.
25% off with code MMHQ25, applied at checkout. Priced in USD - checkout may show the equivalent in your local currency.
View the book and save 25%