Runway & Burn Rate Calculator
Enter your cash balance, monthly revenue, and monthly expenses to see your net burn rate and how many months of runway you have left.
Inputs
Runway is a snapshot, not a guarantee
Net burn is what's actually left over each month after revenue — expenses minus revenue. Runway (cash ÷ net burn) tells you how many months you have left if nothing changes. The moment revenue, expenses, or growth rate shifts, the real number shifts too — this calculator's month-by-month table exists specifically to make that growth assumption visible, since a single "months of runway" figure hides whether it's flat, improving, or worsening.
How to use it
- Under 6 months of runway is generally considered critical — most founders start cutting costs or raising well before hitting this point, since fundraising itself takes months.
- 12-18 months is a common comfort zone that gives room to adjust course without an immediate cash crisis.
- Model a conservative growth assumption, not an optimistic one — runway calculators are most useful as a downside check, not a best-case projection.
Common mistakes
- Assuming a flat growth rate holds for the full projection window — growth (and burn) rarely stay linear for 12-24 months in either direction.
- Excluding one-time or lumpy expenses (annual software renewals, contractor payouts, taxes) from the monthly expense figure, which makes runway look longer than it actually is.
- Confusing net burn with gross burn (total expenses, ignoring revenue) — gross burn matters for understanding cost structure, but net burn is what determines how long the cash actually lasts.
- Looking at runway alone without checking whether that burn is buying growth — the same net burn figure feeds the burn multiple calculator, which asks how much new ARR the cash is actually converting into.
Frequently asked questions
How many months of runway is considered safe?
Under 6 months is generally considered critical — most founders start cutting costs or raising well before then, since fundraising itself takes months. 12-18 months is a common comfort zone that gives room to adjust course.
What's the difference between net burn and gross burn?
Net burn is expenses minus revenue — what's actually left over each month. Gross burn is total expenses, ignoring revenue. Gross burn matters for understanding cost structure, but net burn is what determines how long the cash actually lasts.
Should I use an optimistic or conservative growth assumption for runway?
Conservative. Runway calculators are most useful as a downside check, not a best-case projection — growth (and burn) rarely stay linear for 12-24 months in either direction.