How many months until zero cash, from your bank balance, burn, and revenue.
Runway is how long you can operate before the money runs out: cash ÷ net monthly burn (expenses minus revenue). It's the number that decides whether you're 'default alive' (revenue will cover costs before cash runs out) or 'default dead' - Paul Graham's framing every founder should know.
If your runway is under 6 months, your only job is extending it: cut burn, grow revenue, or raise. Knowing the zero-cash date turns vague anxiety into a concrete deadline.
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