How to Create a Burn Rate and Runway Forecast

Why Burn Rate and Runway Matter

For startups and growing businesses, two metrics reign supreme: burn rate and runway. Burn rate tells you how fast you are consuming cash. Runway tells you how long you can keep going. Together, they form the most critical early warning system for business survival.

Running out of cash is the number one reason startups fail. A clear burn rate and runway forecast prevents this fate.

Calculating Your Burn Rate

Burn rate comes in two flavors, and you need to track both:

Metric	Formula	What It Tells You
Gross Burn Rate	Total monthly operating expenses	What it costs to keep the lights on
Net Burn Rate	Monthly expenses minus revenue	Actual cash loss per month
Runway	Cash balance / Net burn rate	Months until cash runs out

Track both monthly and calculate a three-month rolling average to smooth out fluctuations. Your net burn determines survival, but gross burn tells you what happens if revenue disappears entirely.

Calculating Your Financial Runway

Runway is calculated by dividing your current cash balance by your monthly net burn rate. If you have 600,000 dollars and your net burn is 60,000 dollars per month, you have 10 months of runway.

However, a static calculation assumes constant burn and zero revenue growth. A more useful dynamic runway forecast incorporates projected changes over time.

Building a Dynamic Runway Forecast

Month 1: Start with your current cash balance and actual net burn rate.
Months 2-6: Project revenue growth based on your pipeline. Model planned expense increases.
Months 7-12: Extend projections using growth rate assumptions. Include contingency for unexpected costs.

Plot the projected ending cash balance for each month. The month where that balance hits zero is your runway end date.

Scenario-Based Runway Planning

Build at least three runway scenarios. The spread between your optimistic and worst-case runways shows your financial risk exposure. If the difference is two months, you have a tight range. If it is six months, you have significant uncertainty to manage.

When to Worry About Runway

Begin fundraising when you have six to nine months of runway remaining. The fundraising process typically takes three to six months. If your runway forecast shows less than six months, treat it as an urgent priority.

For bootstrapped businesses, a minimum of three months of operating expenses in cash reserves is considered a healthy safety net.

Extending Your Runway: Three Levers

Increase revenue: Ideal but takes time to materialize.
Decrease expenses: Provides immediate relief but may slow growth.
Raise capital: Extends runway but comes with dilution or debt.

Finntree helps by providing clear visibility into your actual burn rate trends and projecting your runway based on real transaction data.

Key Takeaway: Monitor your burn rate and runway continuously rather than periodically. Early warning gives you time to take action before your options narrow, whether that means cutting costs, accelerating revenue, or beginning a fundraise.