Cash Burn Rate and Runway: Know Your Countdown Clock
Last updated: February 10, 2026
The email from the bank arrived on a Tuesday: account balance $47,000. The founder checked the books. Payroll was $62,000 due Friday. No one had tracked burn rate in three months. By noon, they were calling investors for emergency bridge funding. The company survived, but barely. Most startups that fail cite running out of cash as the cause. Not lack of product-market fit. Not competition. Cash.
Cash burn rate measures how fast your company spends cash each month. Runway tells you how many months remain before that cash runs out. Together, these metrics form the heartbeat of startup financial planning. They dictate when to fundraise, whether to hire, and when to cut costs.
This calculator takes your current cash balance, monthly inflows, and monthly outflows to compute net burn, runway in months, and a projected zero-cash date. Use it to run scenarios, plan fundraising timelines, and make decisions with clear visibility into your financial position.
Net Burn vs Gross Burn
Investors and founders often use the term "burn rate" loosely, but the distinction between gross burn and net burn matters. Confusing them leads to miscommunication and planning errors.
Gross Burn Rate
Total monthly cash leaving the business. Every dollar spent on payroll, rent, software, marketing, and operations counts toward gross burn. It represents your full operating cost regardless of how much revenue comes in.
Net Burn Rate
Gross burn minus cash inflows. This is the actual rate at which your cash reserves deplete. A company with $200,000 gross burn and $150,000 monthly revenue has $50,000 net burn. Runway calculations use net burn.
| Metric | Formula | Use For |
|---|---|---|
| Gross Burn | Total monthly cash out | Understanding cost structure |
| Net Burn | Cash out minus cash in | Calculating runway, planning funding |
When Net Burn Is Negative
If cash inflows exceed outflows, net burn is negative. This means the business is generating cash and growing reserves. Runway becomes unlimited at current rates. Negative net burn is the goal for mature companies and a milestone for growing startups.
Runway in Months and in Dates
Runway is calculated by dividing current cash by monthly net burn. The result tells you how many months remain before cash hits zero. Converting months to a calendar date makes the urgency real.
Runway formula:
Runway (months) = Current Cash / Net Monthly Burn
Zero-cash date = Today + Runway months
Why Dates Matter
Saying "we have 14 months of runway" is abstract. Saying "we run out of cash in April 2027" creates urgency. Work backward from your zero-cash date to set deadlines for fundraising, hitting revenue milestones, or cutting costs.
Target Runway by Stage
Pre-seed companies typically target 12 to 18 months. Seed and Series A companies target 18 to 24 months. Later-stage companies often maintain 24 months or more. These targets give time to hit milestones, recover from setbacks, and raise the next round without desperation.
Fundraising Lead Time
Raising a round typically takes 4 to 6 months from first meeting to wire. Start your fundraising process when you have at least 9 to 12 months of runway remaining. Waiting until month 6 puts you in a weak negotiating position.
Cut Spend vs Grow Revenue
When runway gets short, founders face a choice: reduce costs or increase revenue. Both extend runway, but each has different implications and timelines.
| Approach | Speed | Trade-off |
|---|---|---|
| Cut costs | Immediate to 60 days | Slower growth, potential morale impact |
| Grow revenue | 3 to 12 months | Requires time you may not have |
Cost Reduction Priorities
- Variable costs first: Marketing spend, contractors, and non-essential software can be cut immediately
- Fixed costs second: Rent, committed salaries, and long-term contracts take longer to unwind
- Protect the core: Keep engineering and sales capacity that drives future revenue
Revenue Growth Levers
- Price increases: Often the fastest revenue lever if you have pricing power
- Accelerate sales: Shorten deal cycles and focus on close-ready opportunities
- Reduce churn: Revenue retained is as valuable as new revenue acquired
Example Runway Plan
Example 1: Series A SaaS Company
Situation: $4.2 million cash on hand. Monthly revenue $180,000. Monthly expenses $340,000. Net burn $160,000.
Calculation: Runway = $4,200,000 / $160,000 = 26.25 months. Zero-cash date is April 2028.
Plan: Start Series B process in Q2 2027 (12 months before zero-cash). If revenue grows 8% monthly, runway extends as net burn decreases. If growth stalls, cut $40,000 monthly from marketing to add 5+ months.
Scenario modeling: At current trajectory, reach break-even in month 18 if revenue growth holds. Default alive.
Example 2: Pre-Seed Consumer App
Situation: $320,000 cash from angel round. Monthly revenue $8,000. Monthly expenses $45,000. Net burn $37,000.
Calculation: Runway = $320,000 / $37,000 = 8.6 months. Zero-cash date is October 2026.
Plan: Seed fundraising must begin immediately. Target closing by month 5 to maintain buffer. If raise fails, reduce team from 4 to 2 by month 6 to extend runway to 14 months.
Critical decision: Hire one more engineer now (runway drops to 7 months) or wait until post-raise. Decided to wait.
Sources
For Educational Purposes Only - Not Financial Advice
This calculator provides estimates for informational and educational purposes only. It does not constitute financial, tax, investment, or legal advice. Results are based on the information you provide and current tax laws, which may change. Always consult with a qualified CPA, tax professional, or financial advisor for advice specific to your personal situation. Tax rates and limits shown should be verified with official IRS.gov sources.