Runway

Runway is how many months a startup can keep operating before running out of cash. The formula:

Runway (months) = Cash on hand / Net monthly burn

Net burn = cash going out − cash coming in. For pre-revenue companies, net burn = gross burn (all expenses). For revenue-generating companies, net burn = expenses − revenue collected. For the full calculation walkthrough — gross vs net runway, a real Lucid Motors Q1 2026 worked example, and the Runway Triangle diagnostic — see Cash Runway Formula: How to Calculate It.

Why 18 months is the canonical target

Most venture-backed startups target raising enough to extend runway to ~18 months. The reason: fundraising itself takes 3–6 months end-to-end, and meaningful business milestones (significant ARR growth, product launches, new geographies) take 12+ months. Runway of less than 12 months puts a company into "always fundraising" mode, which compresses execution.

Three runway thresholds founders track

• 18+ months: comfortable, can prioritize the business over fundraising
• 12 months: time to start the next raise; lead investor outreach should begin
• 6 months: critical — bridge financing, cost cuts, or pivot become the priority

Below 3 months, founders typically stop comparing offers and accept what's on the table.

How runway changes

Runway grows in three ways: raise more capital, cut burn, or generate revenue net of cost. The fastest lever is usually cutting burn — headcount accounts for ~70% of typical startup costs, so reducing team or compensation extends runway proportionally. The slowest lever is revenue, which scales over quarters not weeks.

The trajectory caveat: runway vs default alive

Runway is a static number — it assumes burn stays flat and nothing grows. That assumption is what makes it dangerous when read alone. Two companies with an identical 10-month runway can be on opposite sides of survival: one whose revenue is climbing 15% a month will cross into profit before the cash is gone (default alive), while one with flat revenue hits a wall at month 11 (default dead). Runway tells you how long you have; whether that's long enough is the trajectory question Paul Graham named default alive or default dead. Always read a runway figure next to its monthly growth rate — see Default Alive or Default Dead for the crossover math and real 2026 cases.

Related

• Cash Runway Formula: How to Calculate It — the full calculation guide with a real Lucid Q1 2026 example
• Default Alive or Default Dead — the trajectory read: will you reach profit before runway runs out?
• Burn Rate — the denominator of runway
• Unit Economics — whether each customer adds to or subtracts from runway
• CAC — the single largest item in many startups' burn