Runway: what cash runway is and how to calculate it

Runway (or cash runway) measures how many months a company can keep operating on the cash it has, at its current rate of cash burn. It is the financial breathing room of the business: how much time is left before the money runs out if nothing changes.

It sums up, in a single number, the relationship between cash in the bank and how fast it leaves. That is why it sits right next to cash flow and burn: cash is the starting point, burn is the speed, and runway is the time that results from that division.

The math is direct: divide available cash by the monthly net burn.

• Runway = available cash / monthly net burn.
• Available cash is the combined balance of accounts and immediately liquid investments.
• Net burn rate is how much more leaves than comes in each month, after subtracting recurring revenue.

Example: with $1.2 million in cash and a net burn of $100k per month, runway is 12 months. If the company spends more than it earns, the result comes out in months; if it is already profitable, net burn is negative and runway stops being a countdown.

Burn rate and runway are two sides of the same coin. Burn rate measures speed (how much cash disappears per month); runway translates that speed into time (how many months the tank still lasts).

It is worth separating two kinds of burn. Gross burn is all the money that leaves in the month. Net burn subtracts the revenue that comes in, and it is the one that belongs in the runway formula. Confusing the two shortens or stretches runway artificially: using gross burn ignores the revenue that already covers part of the costs.

In the startup world, one rule of thumb has become near consensus: raise enough cash for 18 to 24 months of runway. The logic is to leave plenty of time to hit the milestones that justify the next round, with a margin for surprises and for a fundraising process that usually takes months.

A short runway drains negotiating power: a founder who has to close a round in 60 days accepts worse terms. Investors like Bessemer tend to look not only at how much time the cash buys, but at how efficiently it is converted into growth. A comfortable runway buys a startup the most valuable thing it can have: time to get it right.

There are only three levers to lengthen runway, and it is worth pulling all three at once:

• Cut the burn: reduce fixed costs, renegotiate contracts and pause hiring that does not move revenue.
• Grow revenue: accelerating MRR and reducing churn lowers net burn without cutting anything.
• Improve unit economics: lowering CAC and raising revenue per customer makes every dollar invested return more cash.

The number that ties this together is the burn multiple: how much cash the company burns to generate each dollar of new recurring revenue. The lower it is, the more efficient the growth and the further the same cash carries.

Runway is the clock that sets a startup's pace. It defines the urgency to raise money or to reach break-even, and it shapes almost every big decision: when to hire, how much to invest in acquisition, when to hit the gas or the brakes.

Operators watch runway closely because it separates the company that controls its own destiny from the one chasing money. Private SaaS surveys, such as the one by KeyBanc Capital Markets, track burn and capital efficiency precisely because, in the end, cash runway is what decides who has the time to turn a good product into a good business.