Startup Burn Rate: How Many Months of Runway Do You Actually Have?

Burn rate and runway are two of the most important numbers for any early-stage founder, but they're easy to calculate wrong if you're not consistent about what counts.

Gross burn vs. net burn

Gross burn is your total monthly cash outflow — payroll, rent, tools, everything spent, with no offset. Net burn subtracts any revenue coming in, giving a truer picture of how fast your bank balance is actually shrinking. Founders sometimes quote gross burn when net burn is the more meaningful number for understanding real runway — worth being precise about which one you're citing, especially to investors.

The runway formula

Runway (months) = Current Cash Balance ÷ Net Monthly Burn

A startup with $500,000 in the bank and $50,000/month net burn has 10 months of runway. This simple formula assumes burn stays constant — in reality, burn often increases as you hire, which is why recalculating monthly (not just once) matters.

The common mistake: static, one-time calculations

Runway calculated once at the start of the year becomes stale fast, especially if you're hiring or if revenue is growing/shrinking. A startup that calculated "18 months of runway" in January but has since doubled headcount might actually have 10 months left by June — recalculating monthly is the only way to catch this early enough to act on it.

Why the fundraising timeline math matters more than founders think

Fundraising typically takes 3-6 months from first investor meeting to money in the bank, sometimes longer. A common, painful mistake is starting to raise only when runway drops to 3-4 months — by the time the round closes, the company may have already run out of cash. Most experienced operators recommend starting to raise with at least 6-9 months of runway remaining, precisely to avoid negotiating from a position of desperation.

Levers to extend runway

Beyond raising more money, extending runway comes down to either reducing net burn (cutting costs, slowing hiring) or increasing revenue faster than costs grow. Modeling multiple scenarios — what happens to runway if you make one key hire, or if revenue grows 20% faster than planned — is far more useful than tracking a single static number.

Track your own runway

Use the free Burn Rate & Runway Calculator to see exactly how many months of cash you have left based on your current balance and burn. Pair it with the Break-Even Point Calculator to see how much revenue growth would extend your runway indefinitely.