Guide
Trading Expectancy Explained
Expectancy is the average amount a strategy is expected to make or lose per trade over a large enough sample.
The simple expectancy formula
Expectancy equals win probability times average win, minus loss probability times average loss.
In R terms: expectancy = win rate x average winner - loss rate x average loser.
Expectancy in R, dollars or percent
Expectancy is often easiest to understand in R because each trade is measured relative to the amount risked. A +2R winner means the trade made two times the planned risk, whether that risk was $100 or 1% of account balance.
Dollar expectancy is useful when account rules matter. Prop firm traders may care about how many dollars of drawdown room remain, while personal account traders may prefer percent risk because the account balance is their real capital base.
Example of positive expectancy
A strategy with a 50% win rate, 1.5R average winners and 1R average losers has an expectancy of 0.25R per trade.
This does not mean every trade earns 0.25R. It means the average trade is favorable if the assumptions hold over a large enough sample. For more context, read positive expectancy trading system.
Why win rate alone is misleading
A high win rate can still lose money if losses are too large. A lower win rate can be profitable if average winners are large enough.
This is why expectancy is more useful than asking whether a strategy wins often. It asks whether the average trade is favorable.
Different profiles can have similar expectancy
Expectancy does not tell you how comfortable the path will feel. Two systems can have similar average returns but very different win rates and drawdown behavior.
| Win rate | Avg win | Avg loss | Expectancy | Typical feel |
|---|---|---|---|---|
| 40% | 2.0R | 1.0R | 0.20R | More losing trades |
| 50% | 1.4R | 1.0R | 0.20R | Balanced |
| 60% | 0.8R | 1.0R | 0.08R | Smoother, smaller edge |
Why positive expectancy can feel bad
Expectancy is an average. It does not describe the order of trades. A strategy can have a good average and still open with a drawdown.
Use the trading probability simulator to see how the same edge can produce different equity paths.
Common expectancy mistakes
- Using a win rate from too small a sample.
- Ignoring fees, slippage and execution errors.
- Assuming the average winner and loser will stay stable forever.
- Confusing positive expectancy with a smooth equity curve.
What expectancy does not tell you
Expectancy does not tell you the next trade outcome, the maximum losing streak or the worst drawdown path. It only describes the average trade if the inputs are accurate.
This is why expectancy should be paired with probability tools. A system can be profitable on average and still require enough capital, drawdown room and emotional tolerance to survive normal variance.
Frequently asked questions
What does positive expectancy mean?
It means the average trade is expected to be profitable before costs and execution errors, assuming the inputs are accurate.
Can expectancy change over time?
Yes. Market conditions, execution quality, fees and strategy behavior can all change expectancy.
Is expectancy enough to judge a strategy?
No. You also need sample size, drawdown, losing streaks and execution quality.
Can two strategies have the same expectancy?
Yes. Different win rates and reward/risk profiles can produce similar expectancy but very different emotional paths.
Should I calculate expectancy in R or dollars?
Use R to compare strategy quality across account sizes. Use dollars when you need to understand balance, drawdown room or prop firm account rules.
How do I calculate expectancy quickly?
Use the expectancy calculator with your win rate, average winner and average loser.