Startup Runway Calculator: How Many Months Until You Run Out of Cash?
Quick Answer
Your runway is how many months you can operate before cash hits zero. Runway = (Available cash) ÷ (Monthly burn rate). If you have $100k and burn $10k/month, you have 10 months. Most founders raise new capital 6 months before runway expires. So you need to start fundraising at month 4. Get this wrong and you're in a fire sale.
Why Runway Is Your Scariest Number
Most startups don't fail because of bad product. They fail because they run out of money.
Runway is the countdown to that moment.
If you have 10 months of runway and your fundraising takes 3 months (which it will), you need to start in month 7. That's two months of buffer.
Most founders don't buffer enough. They start fundraising in month 9. By month 10, they're out of options:
- Investors smell desperation (your runway clock is ticking)
- You can only take the first offer
- The valuation is 40% lower than it would've been
- You end up massively diluted
The Runway Formula (Real Talk)
Runway (months) = (Available cash) ÷ (Monthly burn)
But "available cash" isn't your bank balance. It's:
- Current cash
- minus minimum operating cash (buffer for payroll delays, unexpected costs)
- minus committed future expenses (office lease, cloud contracts)
And "monthly burn" isn't just payroll. It's:
- Salaries
- Rent
- Cloud infrastructure
- Tools (SaaS subscriptions)
- Legal/accounting
- Marketing
- minus any revenue you're bringing in
Example: $300k cash, $25k monthly burn
- Simple runway: $300k ÷ $25k = 12 months
- But you need a $20k operating buffer
- Real available cash: $280k
- Real runway: $280k ÷ $25k = 11.2 months
You have 11 months. Start fundraising at month 5.
The Three Runway Phases
As a founder, you live in three phases:
Phase 1: The Safety Zone (Months 1–6)
You have plenty of runway. You can hire, experiment, take risks. You're not under pressure.
Phase 2: The Planning Zone (Months 6–9)
You should be fundraising now. Your pitch deck is polished. You have meetings. Investors are interested. You're comfortable but focused.
Phase 3: The Panic Zone (Months 9+)
Runway is running out. Fundraising is urgent. Investors sense your urgency and lowball. You can't afford to be picky about terms.
Most founders spend Phases 1 and 2 procrastinating on fundraising. They realize they're in Phase 3 when it's too late.
The Mistake: Not Accounting for Fundraising Time
Fundraising takes 3 months (realistic):
- Month 1: Pitch meetings, investor meetings
- Month 2: Due diligence, term sheet negotiation
- Month 3: Legal docs, closing
So if you close a funding round at month 10 (6 months of fundraising efforts starting at month 5), your new capital arrives after your runway expires.
You need to start fundraising BEFORE you're desperate.
Common Runway Mistakes
❌ Mistake 1: Calculating runway but not updating it You calculated 12 months of runway three months ago. You haven't updated it. Maybe burn is higher now. Maybe revenue is up. You're flying blind.
✅ Better approach: Update runway calculation monthly. Use a simple dashboard: (Cash) ÷ (monthly burn) = runway. Track it like you track product metrics.
❌ Mistake 2: Burning faster than expected You budgeted $20k/month burn. But you over-hired, and actual burn is $28k/month. Your 12-month runway becomes 8 months.
✅ Better approach: Track burn weekly. If it's trending higher, cut costs immediately. Hiring is easy, firing is hard.
❌ Mistake 3: Not planning for fundraising overhead While you're fundraising, you're distracted. Your team is slower. Your execution slips. Some startups burn an extra $5k/month during fundraising.
✅ Better approach: Budget extra burn during fundraising period. Add 2 months to your fundraising timeline (so you start earlier).
❌ Mistake 4: Assuming you'll raise on schedule You target a Series A close in month 10. What if it takes until month 13? What if the deal falls through?
✅ Better approach: Plan for the deal to take 3x as long as you expect. If you think 3 months, plan for 9 months. This means starting fundraising much earlier.
Step-by-Step: Calculate Your Real Runway
- Export your actual cash position from your accounting software
- Calculate "safe cash minimum": Enough to cover 2 months of payroll if you had to (emergency fund)
- Calculate "available cash": Total cash - safe minimum
- Export your last 3 months of spending from your accounting software
- Calculate average monthly burn: (Sum of 3 months) ÷ 3
- If you have revenue, subtract it: Monthly burn - monthly revenue = net burn
- Calculate runway: Available cash ÷ net monthly burn
- This is your number. Write it down. Check it weekly.
- Calculate "fundraising urgency date": Runway - 3 months. Start fundraising by this date.
- Run /products/founder-salary-affordability-calculator to model different burn scenarios
- Model scenarios: Current burn, +20% burn (if you hire), -20% burn (if you cut costs)
- Create a runway dashboard your team can see (except maybe the full number)
The Runway Tiers
| Runway | Your Mindset |
|---|---|
| 24+ months | Relaxed. You can think long-term. You can hire. You can experiment. You're in control. |
| 12–24 months | Careful. You're fundraising but not desperate. You can be selective. |
| 6–12 months | Urgent. You need to close funding soon. You're taking calls with any credible investor. |
| 3–6 months | Panic. You're in fire-sale mode. You accept terms you normally wouldn't. |
| <3 months | Death spiral. You're cutting burn to the bone. Likely to fail. |
Most healthy startups operate in the 12–18 month range.
FAQ
Q: How much runway should I target? A: 18 months is ideal (gives you flexibility to fundraise). 12 months is acceptable. Below 12 months, you're under pressure.
Q: What if I'm bootstrapped with no fundraising plans? A: Your runway is infinite if you're profitable. If you're not profitable, calculate when you'll break even. That's your real deadline.
Q: Can I reduce burn to extend runway? A: Yes, but each cut slows growth. Cutting 20% of burn might cut 40% of growth. Model the trade-off.
Q: Should I raise more than I need, just to be safe? A: Maybe. Extra capital gives you buffer and leverage in future fundraising. But it dilutes you more.
Q: How do I know if my burn is "normal"? A: Compare to your stage and category. Series A SaaS companies typically burn $30k–$100k/month. Early-stage pays lower, but also has lower CAC. Use benchmarks from similar companies.
Q: What if I'm running out of runway in 2 months? A: Option 1: Cut burn by 30%+ immediately. Option 2: Raise emergency funding (convertible note, bridge). Option 3: Sell the company or wind down. Most founders choose Option 1 or 2.
The Founder Mindset
Runway is your scoreboard. Not product metrics, not revenue, not growth rate.
Your runway is the thing that keeps you alive.
Update it monthly. Plan fundraising based on it. Make hiring decisions based on it.
If you get to 0 months, game over. So don't.
Use /products/founder-salary-affordability-calculator to model different spending scenarios and understand where your true cash-out date sits.