A strategy can have many winners and still lose money. The distribution of gain and loss sizes, plus costs, determines the arithmetic.

The underlying mechanism

Expected value can be summarized as the probability-weighted average gain minus probability-weighted average loss and friction. Even a favorable average in a sample may be unstable, and rare large losses can dominate realized outcomes.

A target-to-stop ratio describes planned payoff distances, not the probability of achieving either one. A promised 3:1 reward-to-risk ratio may still have negative expected value when the likelihood of hitting the target is small or transaction costs are significant.

How to evaluate it in practice

Record gross and net results, average win, average loss, frequency, largest drawdown and exposure. Test different regimes and look at whether stops behave as intended during gaps or illiquid periods.

Consider an invented simplified strategy with a USD 100 planned loss, USD 200 planned gain and 25% win probability. Its expectation before fees is 0.25 × 200 − 0.75 × 100 = minus USD 25 per trade. The arithmetic highlights why a larger numerical target does not guarantee a profitable method.

Common mistakes and limits

A quoted “three-to-one reward-to-risk” is an intended payoff shape, not a forecast. Execution failures and discretionary exits can change the realized ratio markedly.

Actual losses may exceed planned stop distances because a stop can execute away from its trigger. The SEC’s stop-order bulletin makes this execution distinction clear. Financing, slippage and leverage also change the distribution.

An exercise for careful readers

Calculate the break-even win rate for two hypothetical payoff structures, then repeat after adding a realistic per-trade cost.

Record the realized outcome distribution of many trades rather than assuming the planned target and stop will fill exactly. Estimate net expectancy, drawdowns and uncertainty using rules decided before inspecting the test sample.

Continue your research

Explore the related topic hub, the risk warning and our editorial standards for additional context. External primary-source references appear below this article.