Many traders focus heavily on win rate when evaluating a strategy. While win rate is important, it does not tell the full story about whether a trading approach is actually profitable over time.
A strategy can win most of its trades and still lose money overall. Equally, a strategy with a lower win rate can still produce strong long-term results if profits are larger than losses. This is where expected value, often shortened to EV, becomes important.
Today, we will explain what expected value means in trading, how it is calculated, and why it provides a more realistic view of long-term performance than win rate alone.
What Is Expected Value?
Expected value is a way of measuring what a strategy is likely to produce over a large number of trades. Instead of focusing on individual wins or losses, EV looks at the average outcome over time based on probability and risk-to-reward.
In simple terms, expected value helps answer this question: “If this strategy is repeated consistently over hundreds or thousands of trades, is it likely to make or lose money overall?”
This is why EV is widely used when evaluating whether a strategy has a genuine edge.
Understanding the Formula
The basic expected value formula is:
EV = (Win Rate × Average Win) – (Loss Rate × Average Loss)
For example, imagine a strategy with:
- A 50% win rate
- An average winning trade of £200
- An average losing trade of £100
The calculation would be:
EV = (0.50 × 200) – (0.50 × 100)
EV = 100 – 50
EV = £50
This means that, on average, the strategy is expected to make £50 per trade over a large sample size.
The important point is that profitability comes from the relationship between wins and losses, not just from how often trades win.
Why Win Rate Alone Can Be Misleading
Many beginners assume that a high win rate automatically means a strategy is profitable. This is not always true.
For example, a strategy may win 80% of trades, but if the losses are significantly larger than the wins, the overall result may still be negative.
On the other hand, some trend-following strategies may only win 40% of the time but still remain profitable because winning trades are much larger than losing trades. This is why focusing only on win rate can create unrealistic expectations about performance.
Thinking in Probabilities
Expected value helps traders think in probabilities rather than emotions. No strategy wins on every trade. Even profitable systems experience losing streaks and periods of drawdown.
For example, a strategy with positive EV may still lose several trades in a row. This does not automatically mean the strategy has stopped working.
Over a small sample size, results can vary significantly. Over a larger sample size, the expected value becomes more meaningful. This is why many traders evaluate strategies across hundreds or even thousands of trades rather than judging performance based on short-term outcomes.
The Importance of Sample Size
A strategy tested over ten trades provides very limited information. Over 1,000 trades, patterns become much clearer.
For example, if a strategy has positive EV across a large sample of trades, traders can have greater confidence that the edge is based on probability rather than luck.
This also helps reduce emotional reactions during short-term losing periods because the focus shifts towards long-term performance.
Expected Value and Risk Management
Expected value works closely with risk management. Even a strategy with positive EV can perform poorly if risk is managed badly.
For example:
- Risking too much per trade can create large drawdowns
- Inconsistent position sizing can distort results
- Emotional decisions can prevent the strategy from being executed properly
This is why consistency in execution matters just as much as the mathematics behind the strategy itself.
Using EV in a Practical Way
Expected value is not about predicting the outcome of the next trade. Instead, it helps traders evaluate whether their overall process is likely to produce positive results over time.
For example, traders may use EV when:
- Reviewing a strategy
- Comparing different approaches
- Analysing changes in performance
- Deciding whether an edge is statistically meaningful
This creates a more objective way of assessing trading performance.
Conclusion
Expected value provides a more complete understanding of trading performance than win rate alone. By combining probability, average wins and average losses, it helps traders evaluate whether a strategy is mathematically profitable over the long term.
Understanding EV also encourages traders to think in probabilities rather than reacting emotionally to individual trades.
At Samuel and Co Trading, this type of structured analysis forms part of understanding how trading performance develops over large sample sizes rather than through short-term results alone.
In trading, long-term profitability is not about winning every trade. It is about having a process that produces positive outcomes consistently over time.
