What is Cash Runway?
Cash runway is the number of months your startup can keep operating at its current spending rate before the bank account hits zero. It is the most fundamental survival metric for any startup.
Unlike runway as a general concept, cash runway focuses specifically on liquid cash, not receivables, not projected revenue, not credit lines. It answers one question: how long until we literally cannot pay bills?
Why Cash Runway Matters
Every startup dies the same way: it runs out of cash. Not customers, not ideas. Cash. Founders who track cash runway weekly catch problems months before they become fatal.
Investors ask about cash runway in every board meeting. They want to know you understand your burn dynamics and have a plan before the clock runs out. A founder who says "we have about a year" without precision signals that finances are not under control.
How to Calculate Cash Runway
The basic formula is straightforward:
Cash Runway (months) = Current Cash Balance / Monthly Net Burn Rate
Net burn rate is your total monthly expenses minus monthly revenue. If you spend $100K per month and bring in $40K, your net burn is $60K.
For a more accurate picture, factor in:
- Accounts receivable that will realistically convert to cash
- Known upcoming expenses (annual contracts, tax payments, hiring plans)
- Seasonal revenue fluctuations
Cash Runway Benchmarks
Healthy: 18+ months of runway. You have time to experiment and fundraise from strength.
Comfortable: 12-18 months. Standard operating range for well-managed startups.
Concerning: 6-12 months. Time to start fundraising or cut burn immediately.
Critical: Under 6 months. Emergency mode. Every spending decision must be justified.
Formula
Cash Runway = Cash in Bank / Monthly Net Burn Rate
Monthly Net Burn = Total Monthly Expenses - Total Monthly Revenue
Example
Your SaaS startup:
- Cash in bank: $900,000
- Monthly revenue: $25,000
- Monthly expenses: $75,000
- Monthly net burn: $50,000
Cash Runway = $900,000 / $50,000 = 18 months
You are in a healthy position. If you plan to raise a Series A, start conversations at 12 months of runway remaining so you close the round with 6+ months still in the bank.
Now imagine revenue grows to $45,000 per month while expenses stay flat:
New net burn = $75,000 - $45,000 = $30,000
New Cash Runway = $900,000 / $30,000 = 30 months
Revenue growth directly extends runway. This is why unit economics and CAC payback period matter so much. They determine how fast revenue closes the gap with expenses.
Cash Runway vs Runway
The terms are often used interchangeably, but cash runway specifically emphasizes the cash component. A company might have "runway" when including projected revenue or committed funding, but cash runway only counts money already in the bank. When in doubt, use the conservative number.
How to Extend Cash Runway
- Cut non-essential spending. Every month of extended runway is another month to find product-market fit.
- Accelerate collections. Move from net-60 to net-30 payment terms. Offer annual prepay discounts.
- Raise before you need to. Fundraising from 18 months of runway gets better terms than fundraising from 6.
- Increase revenue. Even small revenue gains at the early stage meaningfully extend runway.
A financial OS built for startups can project cash runway automatically based on live bookkeeping data, replacing the manual spreadsheet approach that most founders outgrow by their seed round.