Win rate is the most quoted trading number and one of the least useful on its own. Expectancy is the number that actually tells you whether a system makes money — because it combines how often you win with how much you win and lose.
The expectancy formula
Expectancy is the average amount you can expect to make (or lose) per trade, across a large number of trades:
Expectancy = (Win% × Average Win) − (Loss% × Average Loss)
Every input matters. A system wins 40% of the time, loses 60%, makes $300 on winners and loses $100 on losers:
- Win side: 0.40 × $300 = $120
- Loss side: 0.60 × $100 = $60
- Expectancy: $120 − $60 = +$60 per trade
A 40% win rate sounds like a losing system. It isn’t — it makes $60 on average every time you pull the trigger. That’s the entire point of expectancy: it stops you from judging a system by any single component. You can walk through the full derivation on our trading expectancy explainer.
Why expectancy beats win rate for judging a system
Win rate answers “how often am I right.” Expectancy answers “does being right, at the sizes I win and lose, actually pay.” Only the second question matters for your account balance.
Traders chase high win rates because being right feels good. But a 90%-win-rate system that risks $500 to make $50 is a slow-motion account killer — one loss erases ten wins. Conversely, trend systems that are wrong most of the time can be enormously profitable because the occasional winner dwarfs the frequent small losses.
A positive expectancy is the minimum bar for a tradable system. If expectancy is negative, no amount of position sizing, psychology, or discipline saves you — you’re playing a game with negative math. If it’s positive, everything else is optimisation. Expectancy is the gate.
Worked example: two systems, same win rate, opposite edge
Two traders both win exactly 50% of their trades. Identical win rates, opposite outcomes:
| System A | System B | |
|---|---|---|
| Win rate | 50% | 50% |
| Average win | $200 | $80 |
| Average loss | $100 | $150 |
| Win side (0.5 × win) | $100 | $40 |
| Loss side (0.5 × loss) | $50 | $75 |
| Expectancy | +$50 | −$35 |
Same win rate, and one is a solid edge while the other bleeds the account. The only difference is the relationship between average win and average loss — the reward-to-risk ratio playing out in real numbers. This is why “I win more than half my trades” tells you nothing until you know your win and loss sizes. It’s also why cutting winners early and letting losers run — the most common discretionary mistake — can flip a System A into a System B without your win rate changing at all.
Expectancy in R: normalizing across instruments and account sizes
Dollar expectancy is fine for one account trading one instrument. The moment you trade multiple instruments or account sizes, dollars stop being comparable — a $60 edge on a micro contract and a $60 edge on a full-size one aren’t the same thing.
The fix is to express everything in R-multiples, where 1R is the amount you risked on the trade. A winner that makes twice your risk is +2R; a full stop-out is −1R. Expectancy in R becomes your average R per trade, a pure number that’s comparable across any instrument, timeframe, or account size:
Expectancy (R) = (Win% × Average Win in R) − (Loss% × Average Loss in R)
An expectancy of +0.3R means you net roughly a third of your risk on every trade, whether that risk is $50 or $5,000. This is the version worth tracking, because it survives changes to your position size. The R-multiple system covers how to log trades in R from the start.
Turning positive expectancy into position sizing and growth
Positive expectancy is potential energy. Position sizing converts it into an equity curve. The same +0.3R edge grows an account slowly at 0.5% risk per trade and aggressively at 2% — but the aggressive version also deepens every drawdown, and prop-firm loss limits punish depth.
Two disciplines turn expectancy into durable growth:
- Size for the drawdown, not the upside. A positive expectancy still delivers losing streaks. Your risk per trade has to be small enough that a normal streak doesn’t breach a prop firm’s daily or trailing loss limit. Keep per-trade risk constant with a position size calculator so one signal is the same risk on every account.
- Feed the edge more trades, not more size. Expectancy is per-trade. More clean, in-plan trades compound the edge; oversizing just amplifies variance. Growth comes from repetition of a positive number.
Tracking expectancy live as trades accumulate
Expectancy computed on ten trades is noise. On a few hundred it’s a genuine measurement. The problem is that markets change — a real edge can decay — so a number you calculated once tells you what was true, not what is.
That’s the case for tracking it live. Shibiki auto-journals every trade and recomputes expectancy per strategy as trades accumulate, wrapping it in a Wilson confidence interval so you can see the range your true edge likely sits in given your sample — not a single misleadingly precise figure. Early on the interval is wide and honest; as your sample grows it tightens, and if real expectancy drifts away from the baseline you calibrated the strategy on, you see it in the data before you feel it in a drawdown. If you’d rather start by hand, the expectancy calculator turns your win rate and average win/loss into a per-trade number in seconds — and unlike a static tool such as Edgewonk, a live edge dashboard keeps that number current as you trade.
Related: Trading expectancy · Expectancy calculator · R-multiple