Expectancy
Expectancy is the average profit or loss you can expect per trade over time. Learn the formula, why win rate alone is misleading, and how to build a positive edge.
Expectancy is the average amount you can expect to win or lose per trade over the long run, given your win rate and the size of your typical wins and losses. It is the single number that tells you whether a trading strategy actually makes money, and it cuts through the illusion of win rate.
If you learn one piece of trading math, make it this one. Let me show you why.
The Formula for an Edge
Expectancy combines two things that matter and that people usually consider separately: how often you win, and how much you win versus lose. The formula ties them together.
Expectancy = (win rate x average win) minus (loss rate x average loss).
A positive expectancy means that, on average, each trade adds to your account over time. A negative one means each trade, on average, drains it, no matter how good any single result feels. The number is your true, long-run edge per trade, expressed in dollars or in the units of risk you take.
Why Win Rate Alone Lies
The most common beginner mistake is judging a strategy by its win rate. Expectancy shows why that is dangerously incomplete.
A high win rate can lose money. Imagine you win 90% of the time, making $10 on each win, but the 10% of trades you lose cost $200 each. Your expectancy is (0.90 x $10) minus (0.10 x $200), which is $9 minus $20, or negative $11 per trade. You win almost every time and still go broke, because your rare losses dwarf your frequent wins.
A low win rate can make money. Now flip it: you win only 40% of the time, but your wins average $300 and your losses average $100. Expectancy is (0.40 x $300) minus (0.60 x $100), which is $120 minus $60, or positive $60 per trade. You lose more often than you win and still profit handsomely, because your winners are much bigger than your losers.
This is why professionals obsess over the size of wins versus losses, the risk-reward ratio, not just how often they are right. Being right feels good; positive expectancy pays.
Building and Using It
Expectancy is not just a scorecard; it is a tool for improving.
Measure it honestly. You get real expectancy from a trade journal of actual results, not from hope. Track your win rate and your average win and loss, and the formula tells you where you truly stand.
Improve the inputs. You can raise expectancy three ways: win more often, make your winners bigger, or make your losers smaller. The last is often the easiest lever, which is exactly why cutting losses with a stop loss is so powerful, it shrinks the average loss in the formula.
Trust the long run. Positive expectancy only pays out over many trades; any single trade is noise. That is why discipline matters: you must keep executing a positive-expectancy plan through losing streaks, because the math only works if you stay in the game. Expectancy is the mathematical heart of a real edge.
- Expectancy is the average profit or loss per trade over time.
- It combines win rate with the size of wins versus losses.
- A high win rate can still lose money; a low one can still profit.
- Raise it by winning more, bigger winners, or smaller losers.
Pop Quiz
Three quick questions to see what stuck. Pick an answer and the explanation shows up right away.
What does expectancy measure?
It combines win rate and the size of wins versus losses into the average result per trade.
Can a strategy with a 90% win rate lose money?
Win rate alone lies: if losses dwarf wins, expectancy can be negative despite winning most trades.
What is often the easiest way to raise expectancy?
Shrinking the average loss with a stop lifts expectancy directly, often more easily than winning more.
Bottom Line
Expectancy is the number that tells the truth about a strategy: the average profit or loss per trade once you account for both how often you win and how much you win versus lose. Positive, and you make money over time; negative, and you bleed, however good it feels along the way.
It exposes the lie of win rate, a high one can still lose, a low one can still profit, and it hands you three levers to improve: win more, win bigger, or lose smaller. Measure it honestly from your journal, and let it turn trading from a feeling into a business.
Keep going: the repeatable advantage it measures is your edge, the balance it depends on is the risk-reward ratio, and you calculate it from your trade journal.