Series disclaimer: Educational content only, not financial advice. Most retail day traders lose money; never risk funds you cannot afford to lose entirely.
If you remember one part of this series, make it this one — and reread it before Part 4. Here's the uncomfortable finding of every serious study of trading performance: entries are nearly irrelevant compared to exits and sizing. Traders with mediocre setups and excellent risk control grind out slow survival; traders with brilliant setups and poor sizing join the 70–90% loser statistics from Part 1. This part teaches the arithmetic that decides which group you're in.
The survival math nobody shows you#
Losses and gains don't cancel symmetrically:
| Loss | Gain required to recover |
|---|---|
| 10% | 11% |
| 25% | 33% |
| 50% | 100% |
| 70% | 233% |
| 90% | 900% |
Drawdowns compound against you asymmetrically. A trader who risks 25% per position needs only two bad trades in a row to face a mountain; one risking 1% needs ten consecutive full losses to lose a quarter of the account — which even a mediocre strategy won't produce if stops exist. Small risk per trade isn't timidity; it's the only reason long streaks of losses (which happen to everyone) remain survivable.
The 1% rule and position sizing#
The working standard: risk a fixed small fraction of the account per trade — 0.5–1% for beginners. Not "invest 1%" — lose at most 1% if the stop is hit.
Position size then derives from three numbers:
Position size = (Account × Risk%) ÷ (Entry − Stop distance)
Example: 100). You buy at 48 (risking 100 ÷ 49 → 100 shares. Wider stop → smaller position. Notice what this does psychologically: every trade risks identical, pre-decided amounts, so no single loss can hurt meaningfully and no single win feels like destiny. Consistency of risk is the foundation consistency of judgment stands on.
Stops: non-negotiable, placed by structure#
A stop-loss is a resting order that exits automatically at a predefined invalidation point. Three rules:
- Every trade gets one, decided before entry. "I'll watch it closely" is not a stop; screens freeze, meetings happen, denial happens.
- Placement comes from the chart, not from your pain tolerance. The stop belongs where the idea is wrong — just beyond the support zone you bought (Part 2), beyond the failed retest — not wherever produces a comfortable share count. Sizing adjusts to the stop, never the reverse.
- Once set, it doesn't move away from price. Widening a stop converts a planned small loss into an unplanned large one; it is the single most common way disciplined plans die.
R-multiples: measuring in risk units#
Normalize outcomes by initial risk. If you risked 200 gain is +2R, breakeven-except-fees is 0R. Thinking in R strips dollar emotion and makes systems comparable regardless of account size.
A trading record becomes simple: a list of R-outcomes. Ten trades of +2R, −1R, −1R, +3R, −1R, +2R, −1R, +2R, −1R, +1R sums to +5R over ten trades with a 40% win rate — profitable despite being wrong more often than right.
Expectancy: the only formula that matters#
Expectancy = (Win% × Avg Win in R) − (Loss% × Avg Loss in R)
- Win 40% averaging +2R, lose 60% averaging −1R →
(0.4×2) − (0.6×1)= +0.2R per trade. Profitable. - Win 80% averaging +0.3R, lose 20% averaging −1.5R →
(0.8×0.3) − (0.2×1.5)= −0.06R per trade. The "high win rate" system bleeds.
This is why win rate alone is marketing. High-win-rate strategies selling losses slowly and winning small feel wonderful and quietly die; low-win-rate strategies cutting losses instantly and letting winners run feel awful and compound. Positive expectancy, executed many times, is the entire game. Nothing else in this series matters without it.
Drawdowns: planning for the inevitable losing streak#
With even a genuinely positive edge, losing streaks arrive by pure chance. At a 45% win rate, a run of five consecutive losses occurs roughly every ~30 trades; eight in a row eventually happens too. At 1% risk that's an −8% drawdown — unpleasant, fully recoverable. At 5% risk it's −34%, demanding the recovery math from the top of this page. Your risk percentage is chosen precisely so the worst normal streak is boring.
Corollaries beginners resist: after losses, risk stays fixed (never "double up to get even" — that's how −8% becomes −40%); after big wins, risk stays fixed (euphoria sizes positions as badly as despair).
The practice assignment that actually builds traders#
Before any real money, ever: open a paper-trading (simulated) account, apply everything above for at least 100 recorded trades, journaling entry/exit reasoning and R-outcome each time. Compute your expectancy at the end. Most people discover their simulated expectancy is negative — which is the single cheapest lesson in finance. Part 4 covers what to do about it: building and validating actual strategies.
