A 55% win rate sounds safe, until you see how often the math hands you seven losses in a row. Drag your win rate and find out.
At a 50% win rate, a 7-trade losing streak is more likely than not across 200 trades. Size your risk so it survives that, not your average day.
Most traders estimate a streak as (loss rate)^N, so a 45% loss rate makes five straight losses feel almost impossible at roughly 1.8%. That number is real, but it answers the wrong question. It’s the chance of losing five in a row starting right now.
Over a hundred trades you start that five-loss countdown a hundred times. Each fresh trade is another roll of the dice. The honest question is: across the whole run, how likely is it that somewherea streak of that length shows up? That’s what the table above computes, a run-length probability over the full sequence, not a single point in time.
The takeaway isn’t doom. It’s that a long losing streak is a normal, expected feature of a profitable edge, not evidence it’s broken. Size your risk so the worst column survives, and a cold streak becomes a Tuesday instead of a blow-up.
This calculator runs on the number you guessed. Tradestar auto-journals every trade and tells you the win rate, streaks and drawdowns you actually have, then coaches you through them.
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