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Risk of ruin calculator

A positive expectancy does not make an account safe — sizing does. This runs a thousand equity paths through your win rate and payoff to find how often the account gets to the loss level you care about.

System
Win/loss ratio 1.50
Risk
How much of the account must be lost to count as ruin.
Each of 1,000 simulated paths runs this many trades.
Risk of ruin
0.4%of paths
Share of 1,000 simulated paths that lost 30% of the account
Risk of drawdown
Paths that touched that loss from a peak
1.2%
Expectancy per trade
win rate × avg win − loss rate × avg loss
25.00 USD
Win/loss ratio
1.50×
System quality
Expectancy measured against one full loss
Solid
Sample size
Reasonable
100 trades
Robust at this size
Fewer than one path in a hundred reached the ruin level over 100 trades.
Risk of ruin by risk per trade
Risk / tradeRisk of ruinRisk of drawdownExpectancy
0.5%0.0%0.0%25.00 USD
1%0.0%0.0%25.00 USD
2% · current0.4%1.2%25.00 USD
3%2.4%13.2%25.00 USD
5%10.6%60.4%25.00 USD
10%38.5%99.6%25.00 USD
Same win rate and payoff as above — only the risk per trade changes. Every figure is 1,000 simulated paths with a fixed seed, so it is reproducible.
How it works

Understanding the numbers

What is risk of ruin?

The probability that a run of losses takes the account down to a defined loss level before the edge has time to assert itself. Both a good system and a bad one can ruin; the difference is how often.

What is expectancy?

Expectancy = win rate × average win − loss rate × average loss. Positive expectancy is necessary but not sufficient: a 60%-win system with a 3:1 payoff still ruins reliably if it risks 25% a trade.

How the simulation works

1,000 independent equity paths of N trades each. Every trade compounds the current equity by +risk% × (win/loss ratio) on a win or −risk% on a loss. The result is the share of paths that touched your loss level.

What the model assumes

Independent trades, a constant win rate and a constant payoff — none of which is exactly true in live markets, where losses cluster. Read the output as a lower bound on the real risk, not as a forecast.

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