Risk of Ruin Calculator
Updated
Having an edge does not stop you going broke — it only makes it less likely. Enter your edge and your bankroll in units and this works out the chance that variance takes everything before the math rescues you.
- Uses the standard deviation we computed ourselves: 1.1322 bets per hand.
- Assumes a flat bet and an unchanging edge — the standard model.
- With no edge, ruin is certain given enough hands. The tool says so.
- Nothing is sent anywhere. It runs in your browser.
Your numbers
The formula, and what it assumes',
For a flat bet with edge e, standard deviation σ and bankroll B units, the chance of ever going broke is approximately:
e−2B·e/σ²
We use σ = 1.1322, which we computed by carrying the second moment through the same solver that produces our house-edge figures. How that was done.
Three assumptions worth knowing. The bet is flat — a counter varying their bet has a different and generally worse risk profile at the same average edge. The edge is constant, which it is not. And it models ruin over an unlimited number of hands, so it is a ceiling rather than a session figure.
If you do not have an edge
Then this calculator does not apply, and the honest answer is simpler: ruin is certain given enough hands. The only question is how long the bankroll lasts, and that is a division rather than a probability.
That is not a reason to avoid playing. It is a reason to decide the amount beforehand.
Keep reading
By Martin Kosek · every number on this site is computed by us, not copied.
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