Position Sizer

Position Sizer

The Position Sizer skill is the ultimate mathematical defense mechanism for your portfolio. Instead of guessing how many shares to buy based on emotion, Pierce calculates your exact position size using your total account equity, your psychological risk tolerance, and the stock's actual mathematical volatility.

What is Position Sizing?

The single fastest way to blow up a trading account is incorrect position sizing.

Most retail traders size their positions based on how "confident" they feel about a stock. If they love a company, they dump 40% of their account into it. If the stock unexpectedly drops 20%, they suffer an unrecoverable 8% drawdown on their entire portfolio from a single bad trade.

Professional traders operate differently. They do not trade based on confidence; they trade based on mathematical risk. Before a professional buys a single share, they know exactly where they are going to cut the loss if they are wrong. They then reverse-engineer the math: "If I am willing to lose exactly 1% of my total account on this trade, and my stop loss is 5% below the current price, exactly how many shares should I buy?"

The Position Sizer skill automates this exact institutional formula. It completely removes the emotion of deciding "how much to buy" and replaces it with cold, hard risk management.

How Pierce AI Executes It

When you ask Pierce to calculate a position size, it acts as a ruthless risk manager, stepping through a strict chronological formula:

1. Parameter Gathering: Pierce establishes your absolute boundaries. It asks for your total portfolio size (e.g., $100,000) and your maximum risk tolerance per trade (e.g., risking 1% of total equity).
2. Absolute Risk Calculation: Pierce translates percentages into real dollars. If you risk 1% of a $100,000 account, Pierce locks in a Maximum Dollar Risk of $1,000. It will size the trade so that if you are completely wrong and get stopped out, you lose exactly $1,000—no more, no less.
3. Stop-Loss Determination: This is the critical variable. Pierce doesn't just guess a random number; it looks at the actual chart. It identifies a logical, technical stop-loss level (e.g., just below the 50-day moving average or structural support).
4. Trade Risk Calculation: Pierce calculates the difference between the current entry price and the technical stop-loss to find the Trade Risk Per Share.
5. Final Share Output: Pierce divides your Total Dollar Risk ($1,000) by the Trade Risk Per Share to give you the exact, mathematical number of shares you should purchase.

Key Metrics & Deliverables

By running the Position Sizer skill, Pierce equips you with an explicit trade execution plan:

• Exact Share Count: The literal number of shares to buy. No guessing required.
• Defined Stop-Loss Limit: A hard price level where the trade thesis is invalidated and you must exit.
• Maximum Dollar Risk: A clear, upfront statement of exactly how much money you stand to lose if the trade fails.
• Capital Allocation Percentage: Pierce calculates how much capital this trade requires (number of shares multiplied by price). If a tight stop-loss mathematically allows you to allocate 50% of your account to one stock, Pierce will flag an "Over-Allocation Warning" to prevent dangerous concentration risk.

Example Prompts & Use Cases

You can actively push Pierce to calculate your risk mathematically using these exact prompts:

• "Calculate a position size for PLTR. I have a $50,000 account and want to risk 1%."
• "Where is a logical technical stop loss for NVDA, and how many shares should I buy risking $500?"
• "I want to buy MSFT. Size the position for a $200k portfolio risking 0.5% per trade."
• "Calculate a safe position size for a highly volatile stock like MSTR. Find a wide stop-loss."

By explicitly providing your account size and risk tolerance, you instantly activate the Position Sizer engine.

Methodology Notes & Limitations

Position sizing is pure math, but the market can still defy logic. Keep these critical limitations in mind:

• Gap Risk: If you set a stop-loss at $90, and the stock closes at $95 on Monday but reports terrible earnings and opens at $70 on Tuesday, your stop-loss will trigger at $70. You will lose significantly more than your predefined Maximum Dollar Risk. The Position Sizer skill cannot protect you from overnight gap-downs.
• Slip Constraints: In fast-moving or illiquid markets, your stop order may not cleanly execute at your exact price. You might suffer "slippage," resulting in a slightly larger loss than calculated.
• The "Fear of Missing Out" Bias: The math might tell you to only buy 10 shares of a stock you love because the logical stop-loss is very wide. Do not let your emotions override the math and buy 100 shares anyway. The Position Sizer is designed to keep you in the game long enough to actually become profitable.

Built for the Survivalist

In trading, defense wins championships. The traders who survive to make millions aren't the ones who pick the best stocks; they are the ones who manage their risk so perfectly that a string of 10 consecutive losing trades barely dents their account. The Position Sizer skill ensures that before you chase alpha, you have unequivocally defined and contained your downside risk.

Note: Position Sizer calculates technical stop-loss parameters requiring live quote data and is included in the PayGo tier and above.