Burn rate and runway for startups: how to measure what is left and what to do when it drops

Published:

Burn rate is the metric that kills startups fastest when ignored. This guide defines gross vs net burn, computes runway with non-linear flows, and lays out decisions for the 12-, 9-, 6-month thresholds.

Open Burn Rate / Runway calculator →

1. Definitions

  • Gross burn: total monthly outflows (payroll, infra, marketing, office, fees).
  • Net burn: outflows minus revenue collected that month.
  • Runway: months you survive at current net burn with today's cash.
net_burn = outflows_month - revenue_collected_month
runway_months = cash / avg_net_burn

2. Average over how many months?

Using last month's burn to project 18 months is a classic mistake.

  • Trailing 3 months: board reporting.
  • Forward 6 months: projection with signed hiring plan.
  • Worst case: no incoming revenue, all contracted costs land.

3. Numeric example

SaaS startup month 18:

  • Cash USD 480k. Payroll 65k. Infra 4k. Marketing 12k. MRR collected 18k.

Gross 81k. Net 63k. Runway 7.6 months — red zone.

4. Decision rules by runway threshold

≥ 18 months

Execute growth plan, measure unit economics, no fundraising pressure.

12–18 months

Start investor conversations. A round typically takes 4–6 months from pipeline to close.

9–12 months

Activate efficiency: cut non-core SaaS, freelance over new hires, annual prepay discounts.

6–9 months

Binary: closing a round in weeks or reducing team. No third option.

< 6 months

Bridge round with existing investors, venture debt, or 30–50% team reduction. Talk to team before 4 months to give transition time.

5. Common errors

  1. Confusing billed MRR with collected.
  2. Ignoring one-time costs.
  3. Excluding taxes (Ecuador payroll +33% employer contribution).
  4. Not modeling churn (5% monthly = 46% MRR loss in 12 months without offset).

6. Connection to valuation

VCs measure capital efficiency with magic number (ARR added / period S&M cost) and burn multiple (net burn / new ARR). Burn multiple < 1.0 excellent, 1.0–2.0 normal, > 2.0 problematic.

7. Related calculators