Runway

Runway is the number of months a startup can operate before running out of cash, calculated as cash on hand divided by monthly net burn. Founders track it monthly (or weekly when cash gets tight), and it is the single most-watched financial metric at an early-stage startup. It is the calendar that determines every other decision: when to raise, when to hire, when to cut, when to push, when to pivot. Running out of runway is the proximate cause behind most stories in Why Startups Fail.

The math:

Runway (months) = Cash on hand ÷ Monthly net burn

A company with $2M in the bank and $100K/month net burn has 20 months of runway. The same company at $200K/month net burn has 10 months. Doubling burn halves the calendar.

Use net burn (cash actually leaving the bank account after revenue offsets spending), not gross burn (total spending before revenue). For pre-revenue companies, net burn equals gross burn. For revenue-generating companies, net burn = gross burn − collected revenue.

Benchmarks by stage (2025 Carta and PitchBook data):

Stage	Target post-close runway	Typical at next-round-raise
Pre-seed → seed	18-24 months	12-15 months remaining when starting seed raise
Seed → Series A	24+ months (preferred)	12-15 months remaining when starting A raise
Series A → Series B	24+ months	12-15 months remaining when starting B raise
Series B+	18-24 months typical	Varies

The 24-month rule (and why):

Investors prefer companies that close with 24+ months of runway because:

• Round-to-round timing: seed-to-Series-A is now ~20 months on average (Carta 2026); 24 months gives buffer for the actual raise (3-6 months).
• Execution time: 24 months lets a team build, ship, and demonstrate traction before the next raise begins.
• De-risking: founders raising with less than 6 months of runway are negotiating from desperation; investors know it and price accordingly.

Calendar vs months, the founder mindset:

A common mistake is treating runway as a static number ("we have 18 months") rather than a date on the calendar. Runway is an exit date: "we run out of cash on March 15, 2027." Every dollar spent moves that date sooner; every revenue dollar booked moves it later. Watching the date makes the urgency real in a way watching "18 months" doesn't.

When runway gets tight:

• 12 months: should already be planning the next raise.
• 9 months: should be actively in conversations with investors.
• 6 months: full raising mode; cutting non-essential spend; preparing bridge round contingency.
• 3 months: emergency mode; pursuing every option (bridge, venture debt, cuts, customer prepays).
• 0 months: ran out.

Stress-testing runway:

Don't run a single point estimate. Run three scenarios:

• Base case: revenue grows as planned, burn stays flat.
• Downside case: revenue grows 50% slower than planned, burn stays flat.
• Crisis case: revenue flat or declining, immediate burn cuts of 30-50%.

If the downside case still gives you 12+ months of runway when you start raising, you're in good shape. If only the base case works, you're banking on execution that hasn't happened yet.

What founders get wrong (specific failure mode): A founder closes a $5M seed with a $250K/month net burn and tells the team they have "20 months of runway." Over the next 12 months, the team grows from 8 to 18 people, burn climbs to $450K/month, and the company hasn't hit the milestone needed for the Series A. At month 12, recalculated runway is 4 months (not the 8 that "20 minus 12" implies, because burn grew). The founder starts the Series A raise with 4 months of runway, every investor sees the desperation, and the round either fails or closes at a brutal valuation. The right discipline: model the burn growth as the team grows, recalculate runway monthly, start raising when there are 12+ months of runway remaining (not 6, not 8).

Related: Burn Rate · Seed Round · Bridge Round · Series A Funding · Cash Flow · Capital Efficiency

FAQ

How do you calculate runway?
Divide current cash on hand by monthly net burn. $2M cash and $100K/month net burn = 20 months of runway. Use net burn (after revenue offsets) for the realistic number; gross burn for the worst-case picture.

How much runway should a startup have?
After a round closes, target 24 months. Anything below 18 months at close is a yellow flag for investors. The seed-to-Series-A timeline has stretched to ~20 months on average (Carta 2026); 24 months at close gives execution time plus raise time.

What's the difference between runway and burn rate?
Burn rate is how much cash you spend each month. Runway is how many months that cash lasts. Runway = Cash ÷ Burn rate. They move in opposite directions: faster burn equals shorter runway.

Should I track runway in months or as a date?
As a date on the calendar. "Months of runway" is an abstraction that lets you avoid the urgency; "out of cash on March 15, 2027" makes the timeline real. The decisions you make change when you're watching a date instead of a number.