How to use the runway calculator
- Enter the cash you have today and everything you spend in a month.
- Enter monthly revenue and how fast it has grown, on average, over the last few months.
- Optionally, add how fast your costs grow (new hires, more servers).
- Read the runway, the break-even month and whether you are default alive, then download the month-by-month CSV.
Runway, burn and default alive
Net burn is what you lose in a month: expenses minus revenue. With flat numbers, runway is cash ÷ net burn: $120,000 of cash, $15,000 of expenses and $4,000 of revenue gives 10 full months. When revenue grows, the gap closes every month, so the calculator steps through the months instead of dividing once.
Paul Graham calls a startup default alive when it would reach profitability on its current numbers before the money runs out. In the example above, flat revenue is default dead, but about 8% revenue growth a month is enough to break even in time. The calculator finds that growth rate for your numbers.
Limits
It projects today’s trend in a straight line. Growth rarely stays steady, so re-run it monthly with fresh numbers. It ignores taxes, annual prepayments and one-off costs; add those to the month they land in if they are large. To see what growth means in customers, use the MRR goal calculator.