Startup Runway Calculator

Formula

• net burn = monthly expenses − monthly revenue
• flat runway (months) = cash ÷ net burn
• growth-adjusted runway simulates each month: cash += revenue − expenses, then grows both by their rates
• breakeven month = first month where revenue ≥ expenses

Methodology

Flat runway assumes nothing changes, which is useful as a floor but rarely realistic. The growth-adjusted model steps forward month by month, compounding revenue and expenses separately, and reports the month cash actually reaches zero.

If revenue grows faster than expenses for long enough, the business crosses into breakeven and runway becomes indefinite. That crossover month is usually the most important date on a startup's plan.

Investors generally want 18-24 months of runway after a round, since raising takes three to six months and you need to reach a milestone before starting.

These are modelling estimates based on standard SaaS metric definitions. Real results depend on your billing data, contract terms and accounting treatment, so reconcile against your finance system before reporting numbers externally.

Example calculation

1. A startup holds $450,000, earns $35,000 a month and spends $85,000.
2. Net burn: $85,000 − $35,000 = $50,000 a month.
3. Flat runway: $450,000 ÷ $50,000 = 9.0 months.
4. With 6% revenue growth against 2% expense growth, the model extends runway to roughly 10 months and shows breakeven arriving shortly after cash would run out — a clear signal to raise or cut.

Frequently asked questions