Expectancy Lab - Updated 2026-07-31

Why a 90% Win Rate Can Still Lose Money

Model expectancy, profit factor, costs, and the effect of one large loss so the win-rate number stops doing all the talking.

Reviewed/updated 2026-07-31 Educational use only Transparent formulas No live prices or individualized advice

Expectancy and Trade Simulator

Run the numbers with your own assumptions

Model expectancy, profit factor, costs, and the effect of one large loss so the win-rate number stops doing all the talking.

Public formula: Expectancy = win rate x average win - loss rate x average loss - per-trade costs.
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Fast answer

A setup that wins $20 nine times and loses $300 once has a 90% win rate, but the ten-trade cycle is still negative before costs.

The useful question is not whether one metric looks good. It is whether the full risk, reward, cost, timing, and recovery math still make sense when the trade behaves badly.

Action checklist

  • Measure average win and average loss separately.
  • Include commissions, spread, and slippage assumptions.
  • Stress-test one or more maximum-loss events.
  • Use expectancy and profit factor beside win rate.

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