Trading Expectancy: The Only Number That Actually Matters

The number that actually tells you if your strategy works

Trading expectancy is the average amount you can expect to win or lose per trade, over a large number of trades, given your win rate and your average win and loss size. The formula: expectancy equals (win rate times average win) minus (loss rate times average loss). Run your own numbers through the Expectancy Calculator to see it directly.

This single number matters more than almost anything else people obsess over when evaluating a strategy, including win rate on its own, which is the number expectancy quietly replaces once you actually understand it.

Why win rate alone is meaningless

A strategy that wins 70% of the time sounds great until you learn its average loss is four times bigger than its average win. Run the math: 0.7 times a small win, minus 0.3 times a much larger loss, and the expectancy can easily land negative. That strategy loses money on average, despite winning most of the time, because the losses that do happen are disproportionately expensive.

The reverse is just as true. A strategy that wins only 35% of the time can be strongly profitable if its average win is large enough relative to its average loss. This is exactly how many trend-following and breakout strategies work: frequent small losses, occasional large wins, and a solidly positive expectancy despite losing more often than winning.

Win rate by itself answers "how often am I right." Expectancy answers "does being right or wrong actually make me money over time." Only one of those questions matters for whether a strategy is worth trading.

A worked example

Take a strategy with a 45% win rate, an average win of $300, and an average loss of $150.

Expectancy equals (0.45 times $300) minus (0.55 times $150), which is $135 minus $82.50, for an expectancy of positive $52.50 per trade. Over 100 trades, that's a theoretical $5,250 in profit, before costs, purely from the math of the edge itself, even though this strategy loses more often than it wins.

Now change one input: keep the same 45% win rate, but drop the average win to $150, equal to the average loss. Expectancy becomes (0.45 times $150) minus (0.55 times $150), which is $67.50 minus $82.50, for a negative expectancy of $15 per trade. Same win rate, same losses, but the strategy is now a guaranteed long-term loser, purely because the win/loss ratio changed.

This is why two traders can report the same win rate and have completely opposite results. Win rate was never the variable that mattered on its own.

How expectancy connects to risk/reward and breakeven win rate

Expectancy, risk/reward ratio, and breakeven win rate are three views of the same underlying relationship. The Breakeven Win Rate Calculator shows the minimum win rate a given risk/reward ratio needs just to break even, before costs. If your actual win rate is comfortably above that breakeven number, expectancy is positive. If it's below, no amount of confidence in the strategy changes the fact that it loses money on average.

This is also why "improving your win rate" isn't automatically the right goal. A strategy with a 2:1 risk/reward ratio only needs to win about 33% of the time to break even. Pushing the win rate higher than necessary, often by cutting winners short out of impatience, can quietly drag expectancy down even while the win rate itself looks like it's improving.

Tracking expectancy honestly

Expectancy is only useful if the inputs come from real, recorded trades, not from memory or from cherry-picked recent results. A trading journal that logs the actual outcome of every trade, not just the ones worth remembering, is the only reliable source for the win rate and average win/loss numbers this calculation depends on. Calculate it from real data, recalculate it periodically as the sample grows, and let that number, not how confident a recent winning streak feels, decide whether a strategy is actually worth continuing.