What Is Expectancy in Trading? How to Calculate Your Edge
Expectancy tells you how much money you expect to make (or lose) on average per trade. A positive expectancy means your strategy makes money over time. A negative expectancy means the market is slowly draining your account, no matter how good individual trades feel. Every trader should know their expectancy before risking real capital.
The Expectancy Formula
The formula is straightforward:
Expectancy = (Win Rate x Average Win) - (Loss Rate x Average Loss)
Here’s a worked example. Your strategy has a 45% win rate, average winning trade of $200, and average losing trade of $100.
- Win Rate = 0.45
- Loss Rate = 0.55 (1 minus win rate)
- Expectancy = (0.45 x $200) - (0.55 x $100)
- Expectancy = $90 - $55
- Expectancy = $35 per trade
This means that over hundreds of trades, you expect to make $35 per trade on average. If you take 20 trades per week, that’s $700/week in expected profit.
You can also express expectancy in R-multiples (units of risk). If you risk $100 per trade, the expectancy is 0.35R, meaning you make 0.35 times your risk per trade on average.
Why Expectancy Matters More Than Win Rate
Many traders obsess over win rate while ignoring expectancy. A 70% win rate feels great emotionally, but if your average win is $50 and your average loss is $200, your expectancy is negative:
(0.70 x $50) - (0.30 x $200) = $35 - $60 = -$25 per trade
You win 7 out of 10 trades and still lose money. Meanwhile, a trend-following system with a 30% win rate but average wins of $500 and average losses of $100 has strong positive expectancy:
(0.30 x $500) - (0.70 x $100) = $150 - $70 = +$80 per trade
This is why professional traders focus on expectancy, not win rate. Your risk-reward ratio and win rate work together to determine profitability. Check our guide on basic trading statistics for more on these relationships.
How to Calculate Your Own Expectancy
You need data. At minimum, 30 trades, ideally 100 or more for statistical confidence.
Step 1: Export your trade history from your broker or trading journal. You need the P&L for every closed trade.
Step 2: Separate winning trades from losing trades.
Step 3: Calculate the average dollar amount of winners and the average dollar amount of losers.
Step 4: Calculate your win rate (winning trades divided by total trades).
Step 5: Plug the numbers into the formula.
If your expectancy is negative, don’t trade the strategy with real money. Go back to backtesting and adjust your rules: tighter stop losses, better entries, larger take profit targets, or filtering out low-probability setups.
Track your expectancy monthly. It will fluctuate, but the trend should remain positive. Use our guide on tracking trading performance to build a comprehensive measurement system.
The Role of Sample Size
Expectancy calculated from 10 trades is nearly meaningless. Random variation dominates small samples. You could flip a coin 10 times and get 8 heads; that doesn’t mean the coin is biased.
At 30 trades, you start seeing patterns. At 100 trades, your expectancy estimate becomes reasonably reliable. At 500+ trades, you can be highly confident in the number. This is why paper trading and backtesting are valuable: they let you generate large sample sizes without risking capital.
Key Takeaways
- Expectancy = (Win Rate x Average Win) - (Loss Rate x Average Loss)
- Positive expectancy means your strategy makes money over time; negative means it loses
- A high win rate doesn’t guarantee positive expectancy; risk-reward ratio matters equally
- You need at least 30 trades (ideally 100+) for a reliable expectancy calculation
- Calculate and track expectancy monthly; don’t trade strategies with negative expectancy
Frequently Asked Questions
What’s a good expectancy number? An expectancy of 0.2R to 0.5R (20% to 50% of your risk per trade) is considered good for retail traders. Professional systems often target 0.3R to 0.7R. Anything above 1.0R is exceptional and should be scrutinized for curve fitting.
Can expectancy change over time? Yes. Market conditions shift, and strategies that worked in trending markets may underperform in ranging markets. This is why ongoing tracking and periodic review are essential.
Does expectancy account for commissions and slippage? Only if you include them in your P&L calculations. Always calculate expectancy using net P&L (after commissions, fees, and estimated slippage) for an accurate picture.
Risk Disclaimer: Trading involves substantial risk of loss. Past performance is not indicative of future results. See our full risk disclaimer.