Cash Burn Rate & Runway Calculator
Estimate your startup's cash burn rate and runway. Enter current cash and monthly inflows and outflows to see net burn, approximate runway, and a simple cash balance projection. Educational use only, not financial advice.
Cash Burn Rate and Runway: Know Your Countdown Clock
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.
How to Calculate Runway
Divide the cash you have on hand by your net monthly burn, which is monthly cash out minus monthly cash in. $600,000 in the bank against $50,000 of net burn is 12 months of runway. Runway uses net burn, not gross burn, because incoming revenue offsets what you spend. If you're collecting more than you spend, net burn is negative and there's no finite zero-cash date. Runway is effectively unlimited at that rate.
Because runway turns on the revenue side of net burn, pin down your recurring revenue and churn before you trust the number. If you sell subscriptions, work out MRR, ARR, and net revenue retention in the SaaS MRR, ARR and churn calculator first, then bring net revenue back here as your monthly inflow.
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
- U.S. Small Business Administration: Cash Flow Management
- U.S. Securities and Exchange Commission: Financial Statements
- SCORE Association: Cash Flow Planning
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 rules, rates, and assumptions, which may change. Always consult a qualified professional for advice specific to your situation, and verify rates or limits with official IRS.gov and related public-source materials.
Common Questions
What is the difference between gross burn and net burn?
Gross burn is total monthly cash outflows regardless of revenue. Net burn is gross burn minus cash inflows. A company spending $100,000 per month with $60,000 revenue has $100,000 gross burn and $40,000 net burn. Runway calculations use net burn because it reflects how fast cash reserves actually deplete.
When should I start fundraising based on my runway?
Start fundraising when you have at least 9 to 12 months of runway remaining. Raising a round typically takes 4 to 6 months from first investor meeting to money in the bank. Waiting until you have 6 months or less puts you in a weak negotiating position and signals desperation to investors.
Why is my runway showing as unlimited or not applicable?
Runway is infinite when net burn is zero or negative. This means cash inflows equal or exceed outflows and your reserves are stable or growing. In this scenario, you are not depleting cash, so there is no finite countdown to running out.
Should I use cash collected or revenue recognized for burn calculations?
Use cash collected, not revenue recognized. Accrual accounting revenue may not reflect actual cash in your account. If customers pay on 60-day terms, your cash position lags your income statement. Burn rate is a cash metric, not an accounting metric.
How do I account for quarterly or annual expenses in monthly burn?
Amortize large periodic expenses across months. If annual insurance is $24,000, add $2,000 to your monthly burn. Alternatively, plan for cash spikes in months when these payments hit. Ignoring lumpy expenses leads to runway surprises.
What burn multiple is considered efficient for a growing startup?
Burn multiple measures net burn divided by net new ARR. A multiple below 1.5x is considered efficient. Between 1.5x and 2x is acceptable for high-growth companies. Above 2x suggests spending is outpacing growth and warrants review. This metric helps investors evaluate capital efficiency.
How can I extend runway without raising more money?
Runway extends when net burn falls, so go after the biggest cash line items first. Cutting a $40,000 monthly burn to $30,000 turns 10 months of runway into more than 13. Delaying non-critical hires, switching annual contracts to monthly, collecting receivables faster, and moving to usage-based infrastructure all help. Growing revenue extends runway too, but slower than cost cuts, because new revenue usually lags the spend that generated it by a quarter or more.
Should runway assume flat burn or growing burn?
Model both. A flat-burn runway assumes today's net burn continues unchanged, which is optimistic if you're hiring or scaling ad spend. A growing-burn model steps expenses up on your actual hiring and spend plan, and it almost always shows runway ending sooner. Investors will run the second version, so run it yourself first. The gap between the two numbers is your margin for slippage.
How much runway should I have after closing a round?
Aim for 18 to 24 months post-raise. That buys roughly a year to hit the milestones that justify the next round, plus the 4 to 6 months a raise itself tends to take. Below 18 months and you're back out fundraising almost immediately. Much above 30 months can mean you took more dilution than you needed. The right target depends on how milestone-driven your next round is.
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Educational tool. Results are estimates.
Educational only. Not individualized financial advice. Consult a qualified financial advisor.
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