Win Rate vs Expectancy: What Actually Drives Profit
A trader can win 70% of trades and still lose money. Understanding expectancy — not win rate — is the key insight that separates professional traders from amateurs.
The Win Rate Illusion
Most beginning traders fixate on win rate. They want to be right most of the time. But win rate alone is meaningless without the corresponding reward-to-risk ratio attached to those wins and losses.
The Expectancy Formula
Expectancy = (Win Rate × Average Win) – (Loss Rate × Average Loss)
This tells you, on average, how much you expect to make or lose per dollar risked. A positive expectancy system makes money over a large sample. A negative expectancy system loses money over a large sample — no matter how many winning streaks you experience.
Examples That Shock New Traders
| Win Rate | Avg Win | Avg Loss | Expectancy |
|---|---|---|---|
| 70% | $50 | $150 | -$10 per trade 🔴 |
| 40% | $200 | $80 | +$32 per trade 🟢 |
| 50% | $100 | $100 | $0 per trade (breakeven) ⚪ |
The 70% win rate system loses money. The 40% win rate system makes money. This is the core insight that changes how traders approach strategy development.
What This Means for Your Strategy
Before trading any strategy live, calculate its expectancy over at least 50 backtest trades. If expectancy is negative, no position sizing system will save it. If expectancy is positive, a proper position sizing system will allow it to compound.