Runway Calculator

Understanding Burn Rate and Runway for Small Businesses

Runway is one of the most important metrics for any business that isn’t yet profitable — and a critical sanity check even for profitable ones. It tells you concretely: if nothing changes, how long until you run out of cash? The answer should inform every major business decision you make.

What Is Burn Rate?

Burn rate is the net amount of cash your business consumes each month. There are two ways to calculate it. Gross burn rate is your total monthly expenses regardless of revenue — it answers “how much are we spending?” Net burn rate is expenses minus revenue — it answers “how much cash are we actually losing each month?” For runway calculations, net burn rate is the relevant figure.

If your monthly expenses are $12,000 and your monthly revenue is $8,000, your net burn rate is $4,000 per month. With $50,000 in the bank, you have 12.5 months of runway at that burn rate.

How Much Runway Do You Need?

The conventional wisdom for startups is 18-24 months of runway. This gives you enough time to execute on your plan, see results, and raise more capital or reach profitability before you run out of options. Under 6 months of runway is a danger zone that demands immediate attention — either cutting costs, accelerating revenue, or raising capital.

For small businesses that aren’t raising venture capital, the math is simpler: you want enough runway to get through lean seasons, unexpected expenses, or a slow patch. Most financial advisors suggest keeping 3-6 months of operating expenses in reserve. Businesses in highly cyclical industries (retail, construction, seasonal services) should aim for the higher end.

Extending Your Runway

Runway extension comes from two levers: increasing revenue or decreasing expenses. Revenue acceleration is usually preferable because it addresses the root cause and doesn’t compromise your operating capacity. Expense cuts can be necessary but can also undermine growth if you cut the wrong things.

When evaluating expense cuts, look for the highest cost-per-value-delivered ratio. Software subscriptions you’re not using, services that could be brought in-house, excess office space, or underperforming marketing channels are common targets. Payroll cuts are more impactful but also more disruptive — usually a last resort.

On the revenue side, consider focusing sales effort on your highest-margin products or services, following up on outstanding invoices, offering prepaid annual contracts at a discount (which brings cash forward), or raising prices — which many small business owners underutilize.

Cash Flow vs. Profitability

A profitable business can still run out of cash. This happens when you have long payment terms (you do the work in January but get paid in March), when you carry inventory that hasn’t sold, or when you’ve made capital investments that haven’t yet generated returns. This is why runway — a cash-based metric — is distinct from profitability.

Conversely, a loss-making business can survive if it has enough cash reserves or incoming investment. Amazon famously burned cash for years while building the infrastructure that would eventually generate enormous profits. For most small businesses, the goal is to reach cash flow positive as quickly as possible — where monthly revenue exceeds monthly expenses — so that the business sustains itself without external capital.

Tracking Runway Over Time

Runway isn’t a one-time calculation — it’s a metric to track monthly. If your runway is shrinking, investigate why: Are expenses growing faster than revenue? Is a receivable overdue? Are you drawing more than the business can support? Catching these trends early gives you time to respond before you’re in crisis mode.

The best way to track runway over time is to maintain accurate, current books. When your revenue and expenses are recorded promptly and correctly, your runway calculation is always based on real data — not estimates or memory. This is the core value of consistent bookkeeping: it gives you the financial visibility to make confident decisions.