The math of ruin: why most bettors blow up before the edge pays

Risk of ruin is not about bad luck. It is about bet sizing combined with variance over time.

Risk of ruin is the probability that a sequence of losses will deplete your bankroll entirely before your edge has time to materialize. It is a function of two things: your edge (expected profit per bet) and your bet sizing (how much you risk per bet relative to your total bankroll). A small edge combined with large bets produces a high ruin probability even if the edge is real.