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Trading Expectancy: The One Number That Says If Your System Works

Expectancy is the average profit or loss you can expect per trade, combining win rate and reward-to-risk. We show the formula, why a low win rate can still win, and how to use it.

ExpectancyTradingWin RateRisk Management

Win rate alone lies to you

"I win 70% of my trades" sounds great β€” but if your losers are five times bigger than your winners, you are losing money. The single number that cuts through the noise is expectancy: the average profit or loss you can expect per trade over the long run. If it is positive, the system makes money; if negative, no amount of discipline saves it.

The formula

Expectancy = (Win% Γ— Average Win) βˆ’ (Loss% Γ— Average Loss)

Example: you win 40% of trades, average winner is $300, average loser is $100.

  • Expectancy = (0.40 Γ— 300) βˆ’ (0.60 Γ— 100) = 120 βˆ’ 60 = +$60 per trade.

So even with a losing win rate of 40%, this system is profitable β€” because the winners are big enough. This is why a low win rate can still win, and why chasing high win rates is often a trap (see realistic profit targets).

Win rate and reward-to-risk are a package

Expectancy shows that win rate and reward-to-risk trade off against each other:

  • High win rate, small winners: works only if you almost never take a big loss β€” one blown stop-loss can erase dozens of small wins.
  • Low win rate, big winners: the trend-following profile β€” many small losses paid for by rare large gains. Emotionally hard, mathematically sound.

Neither is "better." What matters is that the combination produces positive expectancy.

Turning expectancy into money

Expectancy per trade times how many trades you take is your expected profit. That is why frequency and consistency matter, and why position sizing is the multiplier β€” a positive-expectancy system sized sensibly compounds; the same system oversized blows up on a normal losing streak.

How to measure it honestly

  • Pull at least 30–50 real trades from your trading journal β€” not cherry-picked ones.
  • Include fees and slippage; they turn many "positive" systems negative.
  • Recompute periodically β€” markets change and so does your edge. Backtesting gives a first estimate, but live results are the truth.

Conclusion

Expectancy = (Win% Γ— Average Win) βˆ’ (Loss% Γ— Average Loss) is the average result per trade and the real test of a system. A low win rate can still be profitable if winners are large enough, so win rate and reward-to-risk must be judged together. Measure it from real trades including costs, keep it positive, and let position sizing and frequency turn it into compounded profit.

Next step

A positive edge only compounds if you trade it consistently. Let a bot execute every signal the same way.

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