About the Runway & Burn Rate Calculator
This runway and burn rate calculator tells you how long your cash will last. Enter cash in the bank, monthly revenue and monthly operating expenses, and it returns gross burn (total monthly spend), net burn (spend minus revenue), months of runway and the calendar date your balance reaches zero.
It is built for founders planning a fundraise, CFOs updating a board model and anyone deciding whether to hire or cut costs. Simple runway (cash ÷ net burn) assumes nothing changes, which is rarely true, so you can add monthly growth rates for revenue and expenses. The month-by-month simulation then shows whether you reach break-even before the money runs out — being “default alive” — and your lowest cash point.
Most investors advise starting a raise with at least 6–9 months of runway left because rounds often take several months to close. Use conservative growth assumptions, include debt repayments in expenses, and treat any undrawn credit line separately.
With the default inputs, the runway is 1 yr 3 mo. Change any value above to recalculate instantly.
How to use the runway & burn rate calculator
- 1Enter the cash you have in the bank today.
- 2Enter monthly revenue actually collected and total monthly expenses.
- 3Optionally add expected monthly growth for revenue and expenses.
- 4Set the start date so the cash-out date lines up with your calendar.
- 5Read runway, cash-out date and status, and use the chart to plan your next raise.
Formula and method
Gross burn is everything you spend in a month; net burn subtracts the cash you collect from customers. Simple runway divides cash on hand by net burn and assumes revenue and costs stay flat.
When you enter growth rates, the calculator simulates each month: revenue and expenses grow by their monthly rates, and the net cash flow is added to the balance. Runway is the point at which the balance would drop below zero, interpolated within the final month, and the cash-out date adds that many months (a partial month counts as 30.44 days) to your start date. If the balance never goes negative within 120 months, runway shows “Over 10 years”. Break-even is the first month after which revenue covers expenses for every remaining month of the simulation; reaching it before cash runs out is what Paul Graham calls being default alive. Growth rates are applied as constant monthly compounding, which is a simplifying assumption.
- Gross burn
- Total monthly cash spending
- Net burn
- Monthly cash spending minus monthly cash revenue
- Runway
- Months until cash reaches zero
Worked examples
$1.2M in the bank, $80k net burn
Spending $120,000 a month against $40,000 of revenue is a net burn of $80,000. $1,200,000 ÷ $80,000 = 15 months, so starting on 1 October 2026 the cash runs out on 1 January 2028.
Revenue growing 5% and costs 2% a month
Growth looks helpful, but costs grow from a much bigger base: 2% of $120,000 adds more each month than 5% of $40,000. The simulation shows cash running out after about 14.8 months — slightly sooner than the flat 15-month estimate.
Fast growth reaches break-even (default alive)
With revenue compounding at 8% a month, revenue overtakes expenses in month 21. Cash falls to a low of about $114,800 before recovering, so the company never runs out of money.
Pre-revenue startup burning $45k a month
With no revenue, gross and net burn are both $45,000. $500,000 lasts 11.1 months, running out in early September 2027 — so fundraising should already be under way.
Profitable today, but costs grow faster than revenue
Revenue of $100,000 beats $90,000 of costs at first, but costs compounding at 3% a month overtake flat revenue in month 5 (90,000 × 1.03⁴ ≈ $101,300). The early surplus is then used up and cash runs out after about 12.8 months, around 25 October 2027. Because revenue does not stay above costs, break-even shows “Not reached”.
Frequently asked questions
How do you calculate startup runway?+
Divide your cash balance by your monthly net burn (expenses minus revenue). For example, $1.2 million in the bank with $80,000 net burn gives 15 months of runway, assuming revenue and costs stay the same.
What is the difference between gross burn and net burn?+
Gross burn is the total cash you spend each month. Net burn is gross burn minus the cash revenue you collect, so it measures how quickly your cash balance is actually falling.
How much runway should a startup have?+
Many investors suggest raising enough to fund 18–24 months of runway, and starting the next fundraise with at least 6–9 months left, because rounds can take three to six months to close.
What does default alive mean?+
A startup is default alive if, on its current revenue growth and expense trajectory, it reaches profitability before running out of cash. Otherwise it is default dead and depends on raising more money.
Should runway include money I expect to raise?+
No. Base runway on cash you actually have. Model a planned round separately by adding it to cash once it is committed, so you do not over-hire on money that may not arrive.
Results are estimates for educational purposes and are not financial advice. Rates, fees and terms vary — confirm with your lender or a licensed advisor before making decisions.