Position Sizing — How Much to Bet

The Insight Most Investors Miss

You can pick winning stocks 70% of the time and still lose money — if your losers are big and your winners are small. Position sizing decides whether your edge actually compounds.

The pros say it bluntly: "Risk management is everything. Stock picking is a side skill."

The Three Building Blocks

1. Maximum Position Size

A single position should rarely exceed 5-10% of your portfolio. Even a high-conviction pick can fail — fraud, accounting scandal, regulatory shock. No view is worth bankruptcy.

A common framework:

2. Maximum Risk Per Trade

The dollar amount you'd lose if your stop-loss hits. Most pros risk 0.5-2% of total capital per trade.

Example: $100,000 portfolio, 1% risk per trade = $1,000 max loss per position. - Stop is 10% below entry → position size = $10,000 - Stop is 5% below entry → position size = $20,000

This is why traders with wider stops take smaller positions — they're keeping their dollar risk constant.

3. Maximum Sector / Theme Exposure

Even diversified-looking portfolios concentrate in disguise. Cap any single sector at 20-25%, any single theme (e.g., "AI plays") around the same. When one sector crashes, you don't want it to be your whole portfolio.

Kelly Criterion — The Math of Edge

For a bet with a known edge:

Kelly % = W - (1 - W) / R

Where: - W = win probability - R = ratio of average win to average loss

If you win 55% of the time with 1.5:1 reward/risk:

Kelly = 0.55 - 0.45/1.5 = 0.25 → bet 25% per trade

In practice, almost no one bets full Kelly — even small estimation errors blow up. Most investors use half-Kelly or quarter-Kelly for safety.

The deeper lesson: size scales with edge. No edge = no bet. Tiny edge = tiny size. Big edge = big size.

The Pyramid

A simple, robust framework for a 20-30 stock portfolio:

• 5-7 core positions: 5-10% each — high quality, high conviction, long-term holds
• 10-15 satellite positions: 2-4% each — promising but less proven
• 5-10 small bets: <1% each — speculation, learning, optionality

This way, when one of your 1% bets goes 10x, you celebrate. When it goes to zero, you barely notice.

Common Position-Sizing Mistakes

• Going all-in on one idea — even a 70% position eats years of gains when wrong
• Sizing by price, not percent — buying "100 shares" of every stock means equal share count, not equal risk
• Adding to losers without a plan — turns small mistakes into big ones
• Letting winners grow into 30-50% positions — paper gains feel great, until they don't (rebalance!)

The FSL Connection

In FSL, your draft picks are forced into preset weights — but the same lesson applies in real life. The biggest decision isn't which stock you pick — it's how much you put behind it.

Markets reward those who can stay in the game. Position sizing is how you make sure you do.