Profit/Loss Ratio

The profit/loss ratio acts like a scorecard for an active trader whose primary motive is to maximize trading gains. The profit/loss ratio is the average profit on winning trades divided by the average loss on losing trades over a specified time period.

The profit/loss ratio measures how a trading strategy or system is performing. Obviously, the higher the ratio the better. Many trading books call for at least a 2:1 ratio. For example, if a system had a winning average of $750 per trade and an average loss over the same time of $250 per trade, then the profit/loss ratio would be 3:1. A consistently solid profit/loss ratio can encourage a trader to leverage bets on the same strategy in an attempt to generate greater absolute profits. Conversely, an unacceptable profit/loss ratio would lead to an examination of the strategy or system employed to find weak links. Perhaps the trader will decide to abandon a strategy or system altogether if the ratio is not producing sufficient gains or even causing capital losses.

The profit/loss ratio can be an overly simplistic way of looking at performance because it fails to take into account the probabilities of gains or losses for the trades. A concept called average profitability per trade (APPT) can be more insightful. APPT is the average amount a trader can expect to win or lose per trade. APPT is the difference between a) the product of the probability of win and average win; and b) the product of the probability of loss and average loss. As an example, take 10 trades, three of which were profitable and seven were losing. The win probability, therefore, is 30% and loss probability is 70%. Further assume that the average winning trade was $600 and the average losing trade was $300. APPT is (30% x $600) less (70% x 300), or -$30. Thus, even though the profit/loss ratio was 2:1 ($600:$300), the trading strategy is actually a losing one in terms of probability.