Why runway is the number that keeps founders awake
Runway — the number of months until your cash runs out — is the most consequential number for any early-stage company. It determines whether you have time to hit your next milestone, whether you can afford to hire, whether you need to start fundraising now or in six months, and whether a bad month of sales puts you in existential danger. VCs expect 12-18 months of runway after a raise. Below 6 months is a crisis. Above 24 months might mean you are not investing aggressively enough in growth.
This calculator takes three inputs: your current cash balance, your monthly burn rate, and an optional monthly burn growth rate. The basic calculation divides cash by burn to get months of runway. The burn growth option models a more realistic scenario where spending increases each month as you add headcount, increase marketing, and scale infrastructure. A startup burning $50,000/month with 10% monthly burn growth runs out of cash much faster than one with flat $50,000/month burn, because the compounding growth accelerates spending exponentially.
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Runway thresholds and what they mean for your startup
| Runway | Status | Typical Action | Fundraising Implication |
|---|---|---|---|
| Under 6 months | Critical | Cut burn immediately or emergency raise | Very difficult |
| 6 - 12 months | Urgent | Active fundraising, prioritize revenue | Challenging |
| 12 - 18 months | Target | Execute on milestones, begin planning | Standard timeline |
| 18 - 24 months | Comfortable | Invest in growth, optimize later | Strong position |
| Over 24 months | Excess | Consider accelerating investment | May signal under-investment |
How to calculate your startup runway
Enter your current cash balance — the total cash in your bank account as of today, including any undrawn credit lines you plan to use
Enter your monthly burn rate — use net burn (total expenses minus revenue) rather than gross burn (total expenses alone) for accurate runway
Optionally set a monthly burn growth rate — if you are scaling headcount or marketing, enter the percentage your burn increases each month (e.g., 5-15%)
The calculator shows your runway in both months and fractional years, with and without burn growth
Testing runway with startup scenarios
Test a seed-stage startup: $1.2 million in the bank, $80,000/month net burn, no burn growth. Runway is 15 months — right in the target zone. The startup has time to hit product-market fit milestones and begin Series A conversations around month 9-10. If revenue increases and net burn drops to $60,000/month, runway extends to 20 months — even more comfortable.
Now test with burn growth: same $1.2 million, $80,000 starting burn, but 8% monthly burn growth as the startup hires engineers and increases marketing. Runway drops to about 11 months. The compounding effect is significant — by month 8, the burn has grown from $80,000 to over $147,000/month. This scenario shows why flat-burn runway calculations can be dangerously optimistic for scaling startups.
Test a pre-revenue company: $400,000 cash, $35,000/month burn (no revenue to offset), 5% monthly burn growth. Runway is about 10 months. Without revenue, every month of runway costs $35,000 or more. The founder needs to either launch revenue-generating features quickly or begin fundraising by month 5 at the latest.
Common runway calculation mistakes
Using gross burn instead of net burn — gross burn ignores revenue, so it overstates how quickly you run out of cash; net burn (expenses minus revenue) is the correct input
Forgetting one-time expenses — annual insurance, legal fees, conference sponsorships, and equipment purchases can create spike months that drain cash faster than the average burn suggests
Ignoring burn growth — if you are hiring, your burn is not flat; a 10% monthly growth rate means burn doubles roughly every 7 months
Counting committed but unraised capital — runway is based on cash in the bank, not a term sheet or a verbal commitment from an investor
Not updating runway monthly — runway is a living metric; recalculating it each month with actuals catches negative trends early
Runway edge cases and decision-making
The relationship between runway and fundraising timing is critical but often misunderstood. You do not start fundraising when you have 3 months of cash left — that is too late. The fundraising process for a priced round typically takes 3-6 months from first pitch to wire. If you need the money in month 15, you should start pitching in month 9-12. This calculator tells you when you will run out; the fundraising timeline tells you when you need to start.
Burn growth rate is the most underestimated input. Startups that raise a round often increase burn by 30-50% within the first quarter by hiring, expanding office space, and increasing marketing. If you raised $2 million and plan to grow burn by 15% monthly, your runway shrinks dramatically compared to the flat-burn calculation. Modeling burn growth is not pessimism — it is realism about what happens after a fundraise.
Revenue can extend runway but complicates the calculation. If your revenue is growing faster than your burn, your net burn shrinks over time and runway effectively extends. If burn grows faster than revenue, runway shrinks faster than the simple calculation shows. For the most accurate picture, model both revenue growth and burn growth together, though this calculator focuses on the burn side.
Who uses a startup runway calculator
Founders deciding when to start fundraising based on how many months of cushion remain
CFOs building monthly cash flow models and board reports that include runway projections
Investors evaluating portfolio company health during quarterly reviews
Startup operators modeling the impact of hiring plans or marketing spend increases on cash survival
Advisors helping pre-revenue founders understand how long their seed capital will last
Frequently asked questions
Q: What is startup runway?
A: The number of months until your cash runs out at the current burn rate. VCs typically expect 12-18 months of runway to allow time to hit milestones and raise the next round.
Q: Why would burn grow each month?
A: Startups scaling typically add headcount, marketing spend, and infrastructure faster than revenue grows. Setting a burn growth rate (e.g., 10% monthly) models this compounding effect.
Q: What is a healthy runway?
A: 12-18 months is the typical target after raising a round. Below 6 months is critical — you need to raise or cut immediately. Above 24 months may mean you are under-investing in growth.
Q: Should I use net burn or gross burn?
A: Net burn (expenses minus revenue) is more accurate for runway calculations. Gross burn (total expenses) is useful for understanding your absolute cost base.
Q: Is my data uploaded?
A: No — all math runs locally in your browser.
Q: How does burn growth affect runway compared to flat burn?
A: Burn growth compounds exponentially. At 10% monthly growth, burn doubles roughly every 7 months. This can reduce a 15-month flat-burn runway to 10-11 months.
Calculate your runway now
Find out how many months of cash you have with the Startup Runway Calculator. Understand your monthly burn in detail with the Burn Rate Calculator. Evaluate investment returns with the NPV Calculator. Measure growth efficiency with the ROI Calculator or calculate how long investments take to pay back with the Payback Period Calculator.
