Position sizing is the process of determining how many shares, contracts, or units to trade based on your account size and the risk of the specific trade. It’s the most important skill in trading because even the best strategy will fail if position sizes are wrong—too large and you risk ruin, too small and you limit your growth.
- Risk 1-2% of your account per trade maximum—never more
- Position size = (Account × Risk%) / Dollar Risk per share
- Adjust size based on stop loss distance, not conviction level
How Position Sizing Works
Position sizing connects your risk tolerance to each specific trade setup. The key insight is that position size should vary based on where your stop loss is placed, not based on how confident you feel.
Position Size = (Account Size × Risk Percentage) / Dollar Risk Per Share
Dollar Risk Per Share = Entry Price - Stop Loss Price
This formula ensures that regardless of whether you’re trading a $10 stock or a $500 stock, you risk the same dollar amount.
Quick Reference
| Account Size | Risk % | Max Risk $ | Stock Entry | Stop Loss | Position Size |
|---|---|---|---|---|---|
| $25,000 | 1% | $250 | $50.00 | $48.00 | 125 shares |
| $50,000 | 2% | $1,000 | $100.00 | $95.00 | 200 shares |
| $100,000 | 1% | $1,000 | $25.00 | $24.00 | 1,000 shares |
Example Calculation
Let’s calculate position size for a real trade setup:
Trade Setup:
- Account Size: $50,000
- Risk Per Trade: 1% ($500)
- Entry Price: $45.00
- Stop Loss: $42.00
- Dollar Risk Per Share: $3.00
Position Size = $500 / $3.00 = 166 shares
Position Value = 166 × $45 = $7,470 (14.9% of account)
Notice that you’re only risking $500 (1%), but your position value is $7,470. The tight stop loss allows a larger position while maintaining controlled risk.
Position sizing determines how many shares to buy based on your risk tolerance and stop loss distance. Calculate it by dividing your maximum dollar risk by the distance to your stop loss. Always risk the same percentage per trade regardless of conviction.
Position Sizing Methods
1. Percent Risk Method (Recommended)
Risk a fixed percentage (1-2%) of your account on each trade. Most professional traders use this method.
2. Fixed Dollar Risk
Risk the same dollar amount per trade regardless of account size. Simple but doesn’t scale well.
3. Volatility-Based (ATR)
Adjust position size based on a stock’s Average True Range. More volatile stocks get smaller positions.
4. Kelly Criterion
Mathematical formula for optimal sizing based on win rate and payoff ratio. Often too aggressive in practice—most traders use “half Kelly.”
Why Position Sizing Matters
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Survival – Proper sizing ensures you can withstand inevitable losing streaks without account destruction
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Consistency – Same risk per trade means your P&L reflects strategy quality, not random bet sizing
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Psychological control – Knowing your max loss in advance reduces emotional decision-making
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Compound growth – Correct sizing allows your account to grow steadily without catastrophic setbacks
Common Mistakes
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Sizing based on conviction – Feeling confident doesn’t change the probability of being wrong. Use consistent sizing.
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Ignoring stop loss distance – A $100 stock with a $5 stop needs 10× fewer shares than one with a $0.50 stop.
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Not adjusting for volatility – Position sizing in volatile stocks like you would blue chips leads to oversized risk.
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Increasing size after losses – Revenge trading with larger positions accelerates account destruction.
How JournalPlus Tracks Position Sizing
JournalPlus automatically calculates your actual risk per trade by comparing entry price to stop loss. You can see whether your position sizes are consistent across trades, identify when you’re oversizing, and track how position sizing discipline correlates with your overall profitability.
