Runway & Burn Rate: How Long You Have Left

Burn rate is how much cash your startup spends per month. Runway is how many months of cash you have left at that rate. Put them together and you get the most important sentence in early-stage finance: "At our current burn, we have X months before we need to raise or reach profitability." If you can't finish that sentence right now, that's the gap to close today.

People say "burn" to mean slightly different things, so it's worth being precise.

For runway, net burn is usually the number that matters, because it reflects what's really leaving the account. A startup with meaningful revenue burns slower than its raw expenses suggest.

Runway is deliberately simple. That's the point, it's a number you should be able to do in your head.

That example is illustrative, not a benchmark. The right burn and the right runway depend entirely on your stage, your revenue, and your plan. What's universal is that you should know your own version of this equation and update it as the inputs change.

There's no single correct runway, but there's a widely held rule of thumb worth knowing: many investors and founders like to see enough runway to reach the next meaningful milestone plus a buffer to raise, often framed as somewhere around 18 to 24 months after a round. The logic is that you want time to build real progress and time to fundraise without a gun to your head.

Treat that as context, not gospel. A capital-efficient startup with revenue can operate on less. What matters is that your runway is long enough to reach a state, a metric, a milestone, that makes your next raise easier than your last.

When runway gets short, raising isn't the only lever. Founders often forget how much control they have over burn.

→ Cut or delay costs. The fastest lever, and usually the least pleasant. Every recurring cost you remove extends runway directly.

→ Accelerate revenue and collections. Getting paid faster improves net burn without cutting anything.

→ Slow hiring. Payroll is usually the biggest line. Delaying a hire buys runway.

→  Watch for cash shocks. An unplanned tax bill can quietly eat a month. Planning for known obligations protects runway.

Runway and fundraising are two sides of one decision. Your runway tells you when you need to raise, and the smart move is to start well before runway runs out, because raising takes months. Founders who start a raise with a short runway negotiate from weakness. Founders who start with a comfortable cushion negotiate from strength. The runway number is what tells you which position you're about to be in.

→ Know your net burn and runway right now. If you can't state both, stop and calculate them.

→ Recalculate after every major change. New hire, new customer, new cost, new runway.

→ Start raising before you're desperate. Runway tells you when "before" is.

→ Build it on real numbers. Accurate burn depends on accurate cash flow and bookkeeping.

Runway is the closest thing a startup has to a life clock. Knowing it doesn't make the number bigger, but it does mean you get to make decisions with time to spare instead of reacting in a panic. The founders who always know their runway rarely get caught by it.