Ask a casino how a table with a modest house edge — often just a percentage point or two — reliably ends every gambler's night in the house's favour, eventually.
The answer is never one big hand. It's that the gambler keeps playing, keeps sizing bets close to what they can afford, and the small edge compounds over enough hands until ruin is close to mathematically guaranteed.
Risk of Ruin is the formula that describes exactly this — and leverage is the fastest possible way to increase the size of every hand you play.
What Risk of Ruin actually measures
Risk of Ruin (RoR) estimates the probability that a trader, given their win rate, their average win-to-loss ratio, and the fraction of capital they risk per trade, eventually loses their entire tradeable capital — not on one trade, but across a long enough sequence of trades for variance to catch up with them.
The intuitive, dangerous mistake is believing that a positive expectancy strategy (one that makes money on average) can't ruin you. It absolutely can, if you're risking too large a fraction of capital per trade — a long enough losing streak, which will happen eventually to every strategy, can wipe you out before the long-run average ever gets to express itself.
The simplified formula
A commonly used simplified version, for a strategy with edge, is: RoR ≈ ((1 − Edge) / (1 + Edge)) ^ Units, where Edge is roughly your win rate advantage adjusted for payoff ratio, and Units is your total capital divided by the amount risked per trade (i.e., how many consecutive losing trades in a row it would take to wipe you out).
The critical, non-obvious insight sitting inside that formula: Units — how many losses in a row you can survive — dominates the result far more than most traders expect. Doubling your edge helps. Doubling the number of loss-units you can survive (by risking half as much per trade) helps dramatically more, and leverage does the opposite: it shrinks the number of units you can survive, often severely, for the exact same dollar risk.
How leverage collapses your unit count
Say a trader has ₹5,00,000 and risks ₹25,000 per trade unleveraged — 20 units of survivable losses before ruin. Introduce 5x leverage on the same position sizing logic without adjusting down, and a trade that used to risk ₹25,000 in capital terms now risks ₹1,25,000 of effective capital exposure for the same stop distance — the same account can now absorb only 4 consecutive losses, not 20, before ruin. The strategy's edge hasn't changed. The Risk of Ruin has changed enormously.
Why this matters more than any single trade's outcome
No single leveraged trade, viewed in isolation, looks reckless enough to worry about. Risk of Ruin is what happens across the sequence — the tenth trade, the thirtieth, the one where an unremarkable losing streak, well within statistical normal for any real strategy, lands on top of leverage-shrunk unit count and ends the account. The formula doesn't care that you were 'right' on 60% of trades. It cares whether the 40% could line up in a row before your capital ran out, and leverage is the single fastest way to make that pile-up-in-a-row scenario reachable.
Key Takeaway
Risk of Ruin estimates the probability of losing your entire capital across a long sequence of trades, not one trade. Even a genuinely profitable strategy can ruin you if position sizing per trade is too large relative to capital. The number of consecutive losses your capital can survive (Units) matters more than most traders expect — more than the edge itself, in many realistic scenarios. Leverage directly shrinks your survivable-loss count for the same dollar risk, dramatically raising Risk of Ruin without changing your strategy's edge at all.