Position Sizing for Event Risk: A Pre-Earnings Credit Put Spread Strategy

For options traders, earnings season presents a classic high-risk, high-reward scenario. The potential for outsized returns from elevated volatility is alluring, but the threat of a catastrophic gap move is ever-present. When trading credit put spreads—a defined-risk strategy—around earnings, the single most critical decision is not which strike prices to choose, but rather how much capital to risk on the trade. This post details a disciplined framework for position sizing within the "event risk window" of an earnings report, transforming a speculative bet into a managed, portfolio-conscious approach.

The Unique Peril of the Pre-Earnings Trade

Trading a credit put spread before earnings is fundamentally different from trading in a normal, continuous market environment. The primary risk shifts from a gradual "grind" against your position to a binary, overnight gap event. While your maximum loss is technically defined by the spread width, a catastrophic gap-down below your long put can realize that full max loss instantly at the open. This lack of any opportunity to adjust or exit before a large loss crystallizes is what makes position sizing paramount.

The implied volatility (IV) crush that benefits premium sellers after the event is irrelevant if the underlying stock gaps through your strikes. Therefore, the core principle of pre-earnings position sizing is this: Size for the worst-case scenario, not for the premium collected. Your portfolio must be able to absorb the full max loss without significant damage.

A Three-Step Pre-Earnings Position Sizing Framework

This framework prioritizes portfolio-level risk management over trade-level probability of profit. It is designed for the conservative capital preservationist willing to sacrifice potential gain for security.

Step 1: Define Absolute Maximum Risk Per Trade

Before analyzing a single stock, establish a firm, non-negotiable rule for your portfolio. A common and prudent guideline is to risk no more than 1% to 2% of your total trading capital on any single event-risk trade. This is not the margin requirement or buying power reduction; it is the defined max loss of the credit put spread.

Example: If your trading capital is $50,000 and you use a 2% max risk rule, your absolute maximum loss on any pre-earnings credit put spread cannot exceed $1,000.

Step 2: Calculate the Natural Position Size

With your absolute risk limit defined, you can now analyze a specific trade. Let's say you are considering a credit put spread on company XYZ, which is trading at $150 before its earnings report.

You analyze support and decide on a short put at the $140 strike and a long put at the $135 strike for protection.
This creates a spread width of $140 - $135 = $5.00 per share.
Since one options contract controls 100 shares, the maximum loss per contract is: $5.00 * 100 = $500. (This is the width minus the credit received. For sizing, we use the full width as the worst-case scenario).

Your $1,000 max risk from Step 1 allows you to trade: $1,000 / $500 per contract = 2 contracts.
This "natural" size is the maximum number of contracts your risk budget permits.

Step 3: Apply the "Event Risk Discount"

Here is the crucial, often-overlooked step. Trading into a known binary event like earnings warrants an additional layer of conservatism. The natural size from Step 2 is your upper bound. We then apply a discount, typically 50%.

Final Position Size: 2 contracts * 50% = 1 contract.

By trading only 1 contract, you are risking just $500 of your $50,000 portfolio (1%), leaving a buffer for the unexpected. This discount acknowledges that while your analysis might point to a high probability of success, the market's reaction to earnings is inherently unpredictable. It prevents over-commitment to any single thesis.

Integrating Stop Losses in an Event Window

The concept of a traditional stop loss based on the underlying stock price is nearly useless for a pre-earnings credit spread. The gap risk renders it ineffective. Instead, you must use a time-based exit rule.

The Rule: If you have not been proven correct (i.e., the stock is not trading safely above your short put strike) within 2-3 days after the earnings announcement, you should close the position for a manageable loss. Why? The IV crush has now occurred, and the trade's primary edge (selling high IV) is gone. You are now left with a directional bet that is not working. Holding to expiration only increases gamma risk and pin risk for minimal additional time decay. A mental stop loss at a 200-300% of credit received loss level post-earnings can prevent a minor loss from festering into a max loss.

Portfolio Construction: Don't Correlate Your Catastrophes

Even with impeccable single-trade sizing, portfolio risk can accumulate if you put on multiple pre-earnings trades in the same sector or during the same week. A broad market selloff triggered by a major macro event or poor results from a bellwether company can impact all your positions simultaneously.

Portfolio-Level Rules:

Sector Diversification: Avoid having multiple event-risk trades in the same sector (e.g., two semiconductor earnings plays).
Earnings Date Staggering: Do not concentrate all event-risk trades in a single 24-48 hour window. Spread them out across the earnings season.
Overall Event-Risk Capital: Consider an aggregate limit, such as no more than 5-10% of your total portfolio exposed to pre-earnings event risk at any one time.

Practical Example: Putting It All Together

Let's walk through a complete scenario.

Trader Profile: $100,000 trading account, using a 1.5% per-trade risk rule and a 50% event-risk discount.

Trade: AAPL trading at $175 ahead of earnings. Trader sells the $165/$160 put spread for a $0.80 credit.

Step 1 - Absolute Max Risk: 1.5% of $100,000 = $1,500.
Step 2 - Natural Size: Spread width = $5.00. Max loss per contract = ~$420 ($500 width - $80 credit). Natural contract count = $1,500 / $420 ≈ 3.57. Round down to 3 contracts.
Step 3 - Event Risk Discount: 3 contracts * 50% = 1.5 contracts. Final decision: Trade 1 contract.

Risk Outcome:

Max Loss at Expiration: $420.
Actual Portfolio Risk: $420 / $100,000 = 0.42%.
Credit Received: $80.

This trade risks a trivial portion of the portfolio for a modest return. If AAPL gaps down badly, the financial and emotional impact is minimal. The trader lives to trade another day.

The Discipline of Asymmetry

The ultimate goal of this framework is to create a favorable asymmetry in your trading: the financial impact of being wrong (a 0.5%-1% portfolio loss) is far less than the potential financial and psychological damage of being wrong with an oversized position (a 5-10% portfolio hit). By rigidly defining risk first and letting that dictate your position size, you flip the script from "how much can I make?" to "what can I afford to lose?"

In the world of event-risk trading, where outcomes can be binary and swift, protecting capital is not a passive activity—it is an active, disciplined strategy. By applying this pre-earnings credit put spread sizing framework, you ensure that no single earnings report, no matter how surprising, can derail your long-term trading journey.