Backtest expectancy calculator
A backtest is only as good as its expectancy. Enter your win rate, average win and average loss to get expectancy per trade, profit factor and the break-even win rate — the four numbers that decide whether an edge is real.
By Mustafa Bilgic · Published 2026-06-27 · Last updated 2026-06-27
Backtest Expectancy Calculator
Expectancy, profit factor & break-even win rate
The four numbers that tell you if a strategy is worth trading
A backtest spits out hundreds of trades, but its quality boils down to a handful of figures. This calculator turns your win rate, average win and average loss into the metrics that actually decide whether an edge exists.
Expectancy is the average dollars you expect to make (or lose) per trade:
expectancy = (win% × avg win) − (loss% × avg loss)
If it is positive, the strategy makes money on average; if it is negative, no amount of position sizing can save it — sizing controls risk, it cannot manufacture an edge. Profit factor is gross profit divided by gross loss; above 1.0 is profitable, and many traders look for 1.3 to 1.6+ on out-of-sample data as a sign of a robust system. The break-even win rate is the win percentage you would need just to break even at your current payoff ratio — avg loss / (avg win + avg loss) — and the gap between that and your actual win rate is your margin of safety.
A worked example
Take a trend-following bot: 45% win rate, average win $180, average loss $100, over 200 trades. Expectancy = (0.45 × 180) − (0.55 × 100) = 81 − 55 = +$26 per trade. Profit factor = (0.45 × 180) / (0.55 × 100) = 81 / 55 = 1.47. The break-even win rate is 100 / 280 = 35.7%, so a 45% actual win rate clears the bar with room to spare. Over 200 trades the model expects about +$5,200 before fees and slippage. That is a strategy worth forward-testing.
These figures assume your historical fills, win rate and payoff repeat in live trading — they rarely do. Fees, slippage, partial fills and overfitting all erode real expectancy below the backtest. Always validate with forward testing on unseen data, and judge the result on risk-adjusted terms with the Sharpe ratio, not raw profit.
Frequently asked questions
What is trade expectancy?
Expectancy is the average profit or loss you can expect per trade: (win% times average win) minus (loss% times average loss). A positive expectancy means the strategy makes money on average; a negative one cannot be fixed by position sizing.
What is a good profit factor?
Profit factor is gross profit divided by gross loss. Anything above 1.0 is profitable. On out-of-sample data many traders look for roughly 1.3 to 1.6 or higher as evidence of a robust edge, while being skeptical of suspiciously high values that often signal overfitting.
What is break-even win rate?
It is the win percentage you need just to break even at your payoff ratio: average loss / (average win + average loss). If your actual win rate comfortably exceeds it, you have a margin of safety; if it is close, small changes in fills can flip the strategy to a loss.
Why is my live expectancy lower than my backtest?
Backtests assume historical fills, win rates and payoffs repeat, and they ignore or underestimate fees, slippage and overfitting. Real expectancy is almost always lower, which is why forward testing on unseen data is essential before committing capital.