Runway is the amount of time a company has before it runs out of cash, while Burn Rate is the amount of money the company is losing each month.
Quick Answer: For a founder, your runway is your most important metric. If you have 1 million in the bank and you lose 100,000 a month, your runway is 10 months. You must either reach profitability or raise more money before that clock hits zero.
Key Takeaways
- Gross Burn vs. Net Burn: Gross burn is total spending; Net burn is spending minus revenue. Net burn is what actually determines your runway.
- Default Alive vs. Default Dead: "Default Alive" means your current growth trajectory will lead to profitability before your cash runs out.
- The Growth Trap: Many startups increase their "burn" to grow faster, but this increases risk if the fundraising market suddenly cools down.
How do I calculate Runway?
The formula is the ultimate life-or-death metric for a startup:
Runway (Months) = \frac{Total Cash Reserves}{Monthly Net Burn}
If you have 500,000 cash and your monthly expenses are 50,000 while your revenue is 20,000, your net burn is 30,000. Your runway is 500,000 / 30,000 = 16.6 months.
How much runway is 'safe'?
Most venture capitalists recommend maintaining 18-24 months of runway. This gives you 12-18 months to build and grow, and 6 months to run a new fundraising process (which always takes longer than expected).
Try the Tool
Managing burn is about preserving capital. See how the value of your remaining cash is affected by inflation using our Inflation Impact Model.
Expert Insight: The 'Revenue Churn' Factor
Founders often calculate runway assuming revenue stays flat. In reality, you must account for "Churn"—customers leaving. If your churn increases, your net burn increases, and your runway can evaporate weeks earlier than your spreadsheet predicted. Always model a "Worst Case" scenario.
Editorial Expansion: Cash Survival, Growth Efficiency, and Fundraising Timing
Runway tells a founder how many months the company can operate before cash runs out. Burn rate tells the founder how quickly that runway is being consumed. These are not vanity metrics; they determine hiring pace, product scope, fundraising timing, and survival options.
Gross burn and net burn need to be separated. Gross burn is total cash leaving the business each month. Net burn subtracts collected revenue. A company with rising revenue can still be in danger if costs rise faster or collections slow.
Runway is also a negotiating metric. Founders who raise money with only a few months of cash left often negotiate from weakness. A company with 18 months of runway has more options than one with four months.
Worked Scenario: Revenue Growth Hides a Collection Problem
A SaaS company has USD 900,000 in cash, spends USD 120,000 per month, and invoices USD 70,000 per month. On paper, net burn is USD 50,000 and runway is 18 months. But if customers pay slowly and only USD 45,000 is collected each month, cash burn is actually USD 75,000 and runway is 12 months.
That difference changes hiring, fundraising, and marketing decisions. Runway should be based on cash collected, not optimistic invoicing.
Runway Inputs
Input - Use in Model - Risk
Cash balance - Starting runway base - Restricted or committed cash may not be usable
Gross burn - Total cash outflow - Can rise after hiring or infrastructure growth
Collected revenue - Reduces net burn - Invoices may not equal cash received
Fundraising time - Needed before cash runs low - Often takes longer than planned
How to Use This Number in Real Decisions
- Calculate runway from actual cash collections, not only bookings or invoices.
- Maintain a base, downside, and severe downside runway model.
- Tie hiring plans to runway thresholds before offers are made.
- Start fundraising early enough that a delayed close does not force emergency cuts.
Common Mistakes to Avoid
- Using revenue booked instead of cash collected.
- Ignoring churn, refunds, failed payments, and annual contract timing.
- Hiring from an optimistic fundraising assumption.
- Treating one-time cost cuts as a permanent business model improvement.
Editorial Method and Assumptions
FinancialMetrics.report treats every calculator-supported guide as an educational model. The article explains the formula, the inputs, the practical assumptions, and the limits of the result, then points readers to official or reputable sources when tax, payroll, lending, investing, or statutory rules affect the answer.
The examples use simplified figures so readers can understand the mechanics without needing a full advisory engagement. They are not personalized financial, tax, investment, mortgage, legal, or accounting advice. Before acting on a result, users should verify the current rules for their jurisdiction and compare the calculator output with their own documents, payslips, invoices, statements, contracts, or loan disclosures.
For practical use, rerun the relevant calculator after income, rates, fees, contribution limits, tax bands, household costs, business margins, or borrowing terms change. A finance answer is strongest when the formula, source, and real-life constraint all agree.
Practical FAQs
What is a healthy runway for a startup?
Many startups try to keep 12 to 24 months, but the right target depends on growth stage, fundraising market, revenue reliability, and cost flexibility.
Should runway include committed investor money?
Only include cash that is actually available or legally committed under reliable terms. Expected funding is a separate scenario.
What is gross burn?
Gross burn is total monthly cash outflow before subtracting revenue. It shows the cost base of the business.
What is net burn?
Net burn is cash outflow minus collected cash inflow. It is the main number used to estimate runway.
Sources and Verification Notes
- U.S. Small Business Administration: Business planning support (https://www.sba.gov/counseling/plan-your-business/)
- U.S. Small Business Administration: Startup cost planning (https://www.sba.gov/business-guide/plan-your-business/calculate-your-startup-costs)
Financial Expert's View
Runway is a calendar, not just a ratio. Founders should attach dates to decisions: when to cut spend, when to raise, when to pause hiring, and when to change strategy.