Win Rate Is Not Edge: Expectancy, Streaks, and the Numbers That Matter
Why a high win rate can lose money and a low one can compound, the expectancy formula in risk units, and the losing-streak table every win rate should be read with.
A 90% win rate can lose money
Win rate is the most quoted and least sufficient statistic in trading. A system that wins 90% of the time, +0.2R each win, and loses 3R on the other 10% has an expectancy of 0.9 × 0.2 − 0.1 × 3 = −0.12R per trade: it loses, reliably, while feeling excellent almost every day. A system that wins 35% at 3R against 1R losses earns 0.35 × 3 − 0.65 = +0.4R while feeling like failure most of the week.
Expectancy — (win rate × average win) − (loss rate × average loss), in risk units — is the number that actually compounds. Costs subtract from it directly.
Read every win rate with its streak table
Losing streaks are not a sign the edge is gone; they are what any win rate mathematically produces. The chance of a streak of length k on consecutive trades is (1 − p) to the power k, and across hundreds of trades long streaks become near-certainties:
- 50% win rate: a 7-loss streak has ~0.8% odds at any spot — near-certain somewhere in 500 trades.
- 40% win rate: 10-loss streaks stop being surprising over a long record.
- 60% win rate: 5-loss streaks remain routine (~1% per window).
Streaks are a sizing input, not trivia
This is where win rate connects to risk per trade: the streak your win rate will eventually produce, times your risk per trade, is a drawdown you have effectively already scheduled. A 40%-win strategy at 2% risk should expect a 10-loss streak — an 18% drawdown — as a matter of arithmetic, not misfortune. If that number would end your account or your discipline, the risk per trade is wrong for the win rate, however good the expectancy.
Measure yours, not the backtest's
Every number above is only as good as the record it comes from. Backtests overstate; memory overstates worse. A written record of entries, exits, sizes and outcomes — reviewed weekly — is the only source of a win rate and expectancy that describe you rather than an idealization. Small samples lie too: fifty trades put wide error bars on any win rate; treat early numbers as provisional.
Run the numbers yourself
Review the next trade against your own recordCommon questions
What is a good expectancy?
Positive after costs, stable across time and market regimes, on a sample large enough to mean something. A modest +0.15R that holds up over 300 trades beats a spectacular +0.8R measured over twenty. The comparison that matters is against your costs and your drawdown tolerance, not against other traders' claims.
Should I stop trading during a losing streak?
Decide the rule before the streak: many traders halve size after a defined run of losses, or pause after hitting a daily or weekly loss cap. What the arithmetic argues against is improvising the answer mid-streak — the moment of maximum drawdown is the moment of minimum judgment.
Does expectancy change with position size?
Expectancy in risk units does not — size scales the dollars, not the R. What size changes is the path: bigger size means the same streaks cut deeper in percent terms, and deep drawdowns damage the compounding that expectancy promises. That is the whole case for sizing from the streak, not from confidence.
Maximelion is decision support, not financial advice. It does not predict markets, recommend trades, or guarantee outcomes. All figures on this page are arithmetic examples, not recommendations.