Ask a founder how much cash runway they have left and the answer is often, “a few months, I think.” That “I think” is the problem. Your runway —the amount of time your startup can operate before running out of cash— is not just a rough estimate: it is a key metric for understanding when you need to act and how much room you have to do so. Getting it wrong can leave you heading into your next funding round with less leverage than you expected.

You do not need to predict the exact day your cash will run out. What matters is that your runway helps you make decisions: when to start preparing your next round, how much capital you need to fund the next stage of growth, and which milestones you need to have reached before you need more funding. Managed well, runway becomes a key tool for making informed strategic decisions about growth, investment and financing.

It is not how much you spend, but how much time each euro buys you.

The calculation is simple: divide your available cash by your burn rate, or net monthly cash outflow. For example, if you have €600,000 in cash and burn €50,000 a month, you have 12 months of runway.

The formula is straightforward. The hard part is making sure the assumptions behind it are realistic. A common mistake is to build the calculation around revenue that has not materialised yet or an overly optimistic scenario. Ask yourself what your runway would look like if revenue stayed exactly where it is today. If that number makes you uncomfortable, you have already learned something important about your real margin for maneuver.

Build a downside scenario too: what happens if a major sale is delayed, a hire needs to happen earlier than planned, or an expected investment costs more than anticipated? And do not focus only on the number of months. The more useful question is which milestones you need to reach before that cash runs out.

This is where runway starts to become a decision-making tool. Knowing that you have twelve months left is not enough. Ask yourself what needs to be true about your business twelve months from now to justify your next round to investors. If you operate in a regulated sector such as healthcare or insurance, factor in pending certifications, regulatory approvals or integrations with established industry players. These processes often take longer than expected. If you do not build in that extra margin, you risk reaching your next round with less time and less negotiating leverage.

Before setting your target runway, answer four concrete questions

1. Which metric do you need to move for an investor to seriously engage? Define one or two milestones that genuinely change the company’s position, rather than a long list of secondary objectives.

2. How much will it cost to get there? Build your burn from the real decisions you will need to make —team, product, sales, technology, regulation and contingencies— rather than working backwards from an arbitrary runway target.

3. How many months do you realistically need to move that metric, without assuming everything will go to plan? Build in time for the factors you do not control.

4. How much additional buffer do you need if the fundraising cycle takes longer than expected, as is increasingly common in Europe? If a delay of a few months leaves you with no room to react, your runway is probably too tight.

Putting those answers together gives you a runway built on real operating logic, rather than a defensive number chosen by default.

A different way to think about it: runway is not about survival, it is about credibility

A well-managed runway does not answer “how long do I have left?” but “what can I prove before the money runs out?” That shift turns a defensive metric into a planning tool. If you tie your runway to concrete milestones, you can approach your next round from a stronger position, backed by evidence rather than urgency.

Managing runway well does not mean hoarding cash for the sake of caution or putting the brakes on growth. It means knowing what you are buying with each month of burn and preserving enough flexibility to change course if your assumptions do not hold.

A useful rule of thumb: review your runway every month, and again whenever a material assumption changes —a new hire, a commercial delay, an additional investment or a cost overrun. The goal is not to predict an exact date, but to give yourself enough time to avoid making important decisions against the clock.

Every month, the GCO Ventures blog publishes new resources for founders on funding, metrics and strategy. Come back next month for more practical perspectives to help you make better decisions.