Position Sizing: How Much to Allocate Per Stock
Learn position sizing strategies for stock investing, including the Kelly criterion, equal-weight approaches, and how conviction level should drive allocation.
Why position sizing matters
Even the best stock pick can damage a portfolio if the position is too large, and a great idea sized too small barely moves the needle. Position sizing bridges the gap between stock selection and portfolio performance. Getting it right is often more important than finding the next winner.
Common approaches to sizing
- Equal-weight: allocate the same dollar amount to every position
- Conviction-weighted: larger positions in higher-confidence ideas
- Kelly criterion: a formula that sizes bets based on edge and odds
- Risk-parity: size positions so each contributes equal volatility
The Kelly formula suggests betting a fraction of capital equal to (edge / odds). In practice, most investors use a fractional Kelly (e.g., half-Kelly) to reduce volatility and account for estimation error in their expected returns.
Practical guidelines
Many professional investors cap individual positions at 5-10% of portfolio value. Concentrated investors like Buffett may go higher, but only with deep research and a long time horizon. Always consider how correlated your positions are -- five bank stocks at 5% each is really a 25% bet on financials.
Research Before You Size
Build conviction through fundamental analysis before allocating capital.
FAQs
How many stocks should I own?▼
Academic research suggests 20-30 stocks capture most diversification benefits. Concentrated value investors may hold 10-15. The right number depends on your ability to deeply research each holding.
Should I use the Kelly criterion for stocks?▼
Full Kelly is aggressive and assumes you know your exact edge. Most practitioners use half or quarter Kelly to account for uncertainty. It works best as a ceiling rather than a target.
How do I adjust sizing for risk?▼
Consider the stock's volatility, your stop-loss distance, and correlation with existing holdings. A volatile small-cap warrants a smaller position than a stable blue chip, even at equal conviction levels.
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Intrinsic Investor is for education and research only. Not financial advice.