How to Calculate Runway and Burn Rate (and Stop Guessing)

Runway = cash ÷ net monthly burn. Learn to calculate burn rate and runway with worked examples, why net burn is the number that matters, and how to track it live.

Runway is how many months until you run out of money. Burn rate is how fast you spend it. Calculate net burn (monthly expenses minus revenue), then divide your cash by it: Runway = Cash ÷ Net Monthly Burn. Got $240,000 in the bank and burning $60,000 a month? You have four months. That is the whole equation.

The hard part is not the math. It is knowing your real numbers without a spreadsheet you forgot to update, and not finding out the hard way.

What is burn rate?

Burn rate is how much cash your company spends each month. There are two kinds, and confusing them is how founders end up surprised.

Gross burn is your total monthly cash outflow — payroll, rent, software, coffee, all of it — with revenue ignored. It answers "what does it cost to keep the lights on?"

Net burn is gross burn minus the revenue you bring in. It answers "how much are we actually losing each month?" Per Rho, if you spend $80,000 a month and earn $20,000 in revenue, your net burn is $60,000. Same company, two very different numbers — and only one of them tells you how long you have.

What is runway?

Runway is the number of months you can keep operating before you run out of money. It is the metric investors ask about first, and the one that quietly governs every other decision you make.

Pilot defines it cleanly: burn rate is the net cash you spend every month, and runway is how many months you have left before the account hits zero. Their example: $150,000 in cash, $50,000 monthly burn, three months of runway. No drama, just division.

The runway formula (with worked examples)

The formula is one line:

Runway (months) = Current Cash ÷ Net Monthly Burn

Use net burn, not gross. Per Rho, investors and operators focus on net burn when judging financial health, because it accounts for the revenue actually offsetting your spend.

Example 1. You have $240,000 in the bank. You spend $80,000 a month and earn $20,000 in revenue, so your net burn is $60,000. Runway = $240,000 ÷ $60,000 = 4 months.

Example 2. You have $150,000 in the bank and your net burn is $50,000. Runway = $150,000 ÷ $50,000 = 3 months (Pilot).

Two notes that save people. First, if your burn is not steady, use a trailing three-month average instead of last month's number — one slow month makes runway look healthier than it is. Second, runway shrinks the second a new expense lands, so the figure is only as good as how fresh your cash number is.

Why this matters more than any other number

Because running out of cash is the thing that actually kills companies. Not bad ideas, not weak teams — empty bank accounts.

CB Insights' analysis of why startups fail ranks "ran out of capital" as the single most-cited cause, showing up in 70% of failures, with a median of just 22 months between a startup's last raise and shutdown. Poor product-market fit is next at 43%. Note the order: capital depletion is usually the final cause of death, not the root problem — but it is the one that ends the story.

It is not only a venture problem. A February 2026 Revenued SMB Economic Outlook survey of 307 owners found 62.9% have fewer than 90 days of cash runway. Worse, 33.9% have less than one month of operating cash if revenue slows. In the same survey, 72.6% said cash flow management is harder today than a year ago.

The thin-runway problem clusters among smaller operators. A Bluevine survey of 774 US business owners found 39% have less than one month of operating expenses on hand, and 51.3% would need to tap emergency reserves within 48 hours to make payroll. The point is not to scare you. It is that runway is the one number you cannot afford to guess at — and most people are.

How much runway should you have?

The classic answer is enough to reach your next milestone with margin to spare. The classic number is 18 to 24 months.

The logic, laid out by NYU's Entrepreneurial Institute: a fundraise takes roughly six months to close, and you need 12 to 18 months of execution to hit the milestones that justify the next round. Raise only 12 months of cash and you are back out fundraising in six, with almost no time to make progress. Add it up and you want 18 to 24 months in the bank the day a round closes.

The harder the funding environment, the longer the runway you want — because the next round always takes longer than the last one did. If money is tight, plan for the slow raise, not the fast one.

How to track runway without a spreadsheet

The reason most founders are guessing is that a spreadsheet is a snapshot, not a live view. The moment you close the tab, it is out of date.

Enty puts it plainly: static cash-flow documents only work if you have time to update them by hand and do not need real-time data. Almost nobody meets both conditions. Meanwhile your cash is scattered — among small business owners who keep personal and business accounts separate, 44% use different banks, and many run two or three banking relationships at once. Tracking runway by hand means reconciling all of that from memory.

This is not just a small-business quirk. The 2019 PwC Global Treasury Benchmarking Survey found roughly 26% of global corporate cash is not visible to treasury on a daily basis — at companies with entire finance departments. If they cannot see a quarter of their cash, the solo founder with a spreadsheet and three bank logins does not stand a chance.

The fix is the one those treasury teams reach for: connect the accounts directly, let software pull live balances, and compute burn and runway automatically. No manual updating, no stale tab, no math at midnight.

The honest part

This is what StartupStarter Finance does. It connects your live bank data through Plaid and computes runway, burn, MRR, and your P&L automatically — so the number you see is the number that is true right now, not the one from the spreadsheet you last touched two weeks ago. Ask the S2X co-pilot "how much runway do I have?" and it reads the real balances and answers, instead of telling you to go find out.

A dashboard will not change your fundamentals. If your net burn is $60,000 and you have $120,000, you have two months whether or not anyone is watching. But knowing it early — while you still have time to do something — is the part that counts. The math was never the problem. The guessing was.

FAQ

What is the difference between gross and net burn rate?

Gross burn is your total monthly cash outflow with revenue ignored — everything it costs to operate. Net burn is gross burn minus monthly revenue, the amount you are actually losing each month. Per Rho, $80,000 in expenses minus $20,000 revenue equals $60,000 net burn.

Which burn rate should I use to calculate runway?

Net burn, always. Runway measures how long until you run out of money, and revenue extends that timeline, so you subtract it. Rho notes operators and investors focus on net burn when judging financial health. Gross burn answers a different question: total operating cost.

How often should I check my runway?

More often than you think — ideally continuously, because runway shrinks the moment a new expense clears. A spreadsheet checked monthly is already stale. Given that 62.9% of owners have under 90 days of runway, waiting for a quarterly review is how surprises happen.

How is runway different from being profitable?

Runway assumes you are losing money and counts how long the cash lasts. Profitability means revenue exceeds expenses, so net burn is zero or negative and runway is effectively infinite. You can have generous runway and still be unprofitable — you are just funding the losses with cash in the bank.

What counts as a healthy runway?

Classically, 18 to 24 months after a raise — about six months to fundraise plus 12 to 18 months of execution, per NYU's Entrepreneurial Institute. In a tighter market, plan toward the longer end, since rounds take longer to close than they used to.