If You Can’t Explain the Contract, You Can’t Size It

Risk is not “one lot” or “one contract”. Risk is P&L per unit move relative to your equity.

Contract specs convert price movement into money movement. If you don’t know that conversion, you can’t control risk, and you can’t compare trades across instruments.

Many retail blowups are just hidden unit errors: trading a product where one ‘small’ move is actually huge in account terms.

Risk note: most blowups are not one mistake, they are a stack. The first error is small. The second is emotional. The third is leverage.

• Define a max loss per day/week that forces a stop, not a “goal”.
• Keep a volatility buffer: size for the worst recent range, not the median.
• Assume correlation rises when you most need diversification.

Size by habit (lots/contracts) → misread pip/tick value → true risk is larger than planned → normal move becomes large loss → margin stress → liquidation.

How it kills accounts:

1. Small loss triggers a “fix-it” trade.
2. Exposure creeps up across correlated positions.
3. A routine streak arrives.
4. Drawdown forces behavior change (revenge sizing / avoidance).
5. One tail event finishes the job.

Before entry, compute: (stop distance × $/pip or $/tick) = $ risk.
Use notional exposure as the sanity check.
If you can’t compute it quickly, you shouldn’t trade it quickly.

Rule that survives:

• Cap total heat (open risk), not just per-trade risk.
• After drawdown, reduce size automatically.
• Plan the gap: size as if stops can slip.

You treat gold or an index like FX and assume the same ‘lot’ meaning. A routine move turns into a multiple-R hit because the tick value was larger than you assumed.

Tell: if you “need” this trade to work to recover, your size is too large.

Size is arithmetic

Confident sizing without unit math is how “normal” days become catastrophic.

Related: Margin is not risk and Costs are a strategy.

Glossary: leverage, margin, R-multiple.

Field checklist

• Define max heat (total open risk). You can’t manage what you don’t cap.
• Keep a free-margin buffer that survives a normal shock and a bad fill.
• Scale down after drawdown. Your job is to stop the bleed, not to win it back.
• Treat correlated positions as one position.
• Plan the gap: what happens if price jumps through your stop?