What Is Expectancy in Trading?

Trading expectancy is the estimated average profit or loss per trade for a defined process. It combines the probability and size of winning and losing outcomes. Expectancy = (win probability × average win) − (loss probability × average loss) The same formula can be expressed in currency, points, or R-multiples. Use absolute values for the average win and average loss in the formula.

Worked example

Assume 100 comparable trades produce:

• 45 wins with an average gain of 1.6R;
• 55 losses with an average loss of 1.0R.

Expectancy = (0.45 × 1.6R) − (0.55 × 1.0R) = 0.17R per trade Before costs, the estimated expectancy is +0.17R. If average spreads, commissions, slippage, and financing equal 0.08R per trade, net expectancy falls to approximately +0.09R. A positive estimate means the historical or modeled average is above zero. It does not guarantee that the next trade, month, or live sample will be profitable.

What expectancy includes

• win probability;
• average gain on winners;
• loss probability;
• average loss on losers;
• transaction and financing costs;
• live execution differences;
• the effect of rules such as partial exits or trailing stops.

Position size changes the currency impact of expectancy and the account’s variance. It should not be used to make a negative expectancy appear positive.

Why win rate is insufficient

A strategy can win often and lose money if its occasional losses are much larger than its typical gains. A lower-win-rate strategy can be profitable when average wins are sufficiently large. Expectancy connects the two dimensions.

Estimation problems

An expectancy estimate can be misleading when:

• the sample is small or selectively chosen;
• different setups are pooled together;
• the strategy was optimized on the same data used for evaluation;
• costs or rejected trades are omitted;
• market conditions have changed;
• live execution differs from the test;
• outcomes are dependent or dominated by one outlier.

Report the sample definition, time period, costs, and uncertainty instead of presenting one number as permanent.

Expectancy and prop accounts

Two strategies can have equal expectancy and very different probabilities of violating a daily or trailing drawdown rule. Evaluate expectancy together with maximum drawdown, losing-streak distribution, time under water, total open risk, and simulated breach probability.