Forecasting & Risk · 2 min read
VaR for founders — the worst month you should plan for
Banks have priced tail risk for decades. Founders running variable AI spend need the same tool: not "what will I probably burn," but "how bad is the bad case.
By Akhil Anand · August 26, 2026
Every founder plans around the expected case. "We'll burn about $40K a month." That's the median — the number in the middle of your outcomes. It's also the number that will not be true in your worst month, which is precisely the month that decides whether you survive.
What VaR actually means
Value-at-Risk answers a sharper question than "what's my average burn?" It answers: at a given confidence level, how bad does it get?
A 95% monthly VaR of $70K means: in 19 months out of 20, your burn stays under $70K. One month in twenty, it's worse. That's not a doomsday figure — it's the line you should be able to absorb without a fire drill.
For a fixed-cost business, VaR is boring; costs barely move. For an AI-native business with usage-driven spend, it's the number that separates "we had a spiky month" from "we didn't make payroll."
P50 is not your planning number
The median (P50) tells you the typical month. But you don't run out of money in a typical month. You run out in the tail. Planning runway off P50 is like buying a boat for the average wave height.
Plan operations around the median. Plan survival around the tail. Confusing the two is how a "fine" runway becomes an emergency raise.
CVaR: how bad is bad?
VaR tells you the threshold you'll breach 5% of the time. It doesn't tell you how far past it you'll go. That's Conditional VaR (CVaR) — the average burn given you're in that worst 5%. If your VaR is $70K but your CVaR is $110K, the bad months aren't just bad, they're violent, and you need more cushion than the threshold suggests.
None of this requires a quant team. It requires modeling burn as a distribution and reading its tail — P5/P50/P95, VaR, CVaR — instead of collapsing it to one comfortable average. The expected case tells you how you'll probably do. The tail tells you whether you'll be around to find out.