Runway is the one startup metric with a hard deadline attached. This burn rate calculator takes cash in bank, monthly spend and monthly revenue, and tells you how many months you have — and how urgent your next raise is.
The formula
Net burn = monthly spend − monthly revenue, then Runway = cash ÷ net burn. Revenue counts: a startup spending $200K and earning $50K burns $150K net, not $200K. If revenue covers spend, burn is zero and runway is infinite — you’re default-alive.
Worked example
$2M in the bank, spending $200K/month, earning $50K/month: net burn $150K, runway = 2,000 ÷ 150 = 13.3 months. Comfortable? Only on paper — fundraising takes 3-6 months, so this founder should start conversations within the next quarter, not next year.
How to read the result
The working rule: 18+ months after a raise is healthy; under 12 means start raising now; under 6 means raising from weakness — the worst negotiating position in startups. The honest caveat: burn is rarely flat. Hiring plans, annual contracts and churn all bend the line, so recompute monthly, and pair this with LTV/CAC to know whether the burn is buying efficient growth.
What's the difference between gross and net burn?
Gross burn is total monthly spend; net burn subtracts revenue. Runway should always use net burn — ignoring revenue understates your position.
How much runway should a startup have?
Raise enough for 18-24 months. Start the next raise with at least 9-12 months left, because closing a round typically takes 3-6 months.
What is default alive?
A company whose revenue growth will reach profitability before the cash runs out — it survives without raising again. Default dead is the opposite.
Should runway include committed but unspent costs?
Yes — signed leases, annual contracts and agreed hires are real. Model runway on forward spend, not just last month’s bank statement.