Position Sizing for Earnings

Position sizing is where earnings trading discipline lives or dies. A profitable trading system with poor position sizing will eventually blow up an account. A mediocre trading system with disciplined position sizing will survive and compound. On earnings day, position sizing is doubly critical because the nature of the risks—gap risk, IV crush, execution slippage—makes standard position sizing formulas dangerously optimistic.

The fundamental principle of position sizing is that you should risk only a small fraction of your account on each trade, even if the expected value is positive. For earnings, the position size should be inversely proportional to the gap risk: the larger the potential overnight gap, the smaller the position should be. Yet most retail traders size inversely to probability of profit, making their largest bets on the lowest-conviction trades.

Quick definition: Position sizing for earnings determines how many contracts, shares, or dollars to allocate to a single trade based on your account size, risk tolerance, expected value, and maximum acceptable loss.

Key takeaways

• Standard Kelly criterion and fixed fractional sizing must be adjusted downward for earnings due to gap risk and IV crush
• Gap risk should reduce your position size by 20–50% compared to intraday trading of the same instrument
• If a single earnings trade can lose more than 2–3% of your account, the position is too large
• The worst earnings trades are often the largest because they offer the highest probability of profit (low expected value per unit)
• Half-Kelly or quarter-Kelly is safer than full Kelly for earnings because it reduces volatility and drawdowns
• Monitor position size against both account size and against your maximum acceptable daily loss

Why Standard Position Sizing Fails on Earnings

The Kelly criterion, the most academically rigorous position sizing formula, is derived from gambling theory and assumes that your edge (probability and win/loss ratio) is correctly estimated. For earnings, this assumption breaks down spectacularly.

The Kelly formula is:

f* = (p × b - q) / b

Where:

• f* = the fraction of your bankroll to bet
• p = probability of winning
• q = probability of losing (1 - p)
• b = odds received (profit if you win / loss if you lose)

For example, if you have a trade with a 55% win rate, risking $1 to make $2 (b = 2):

f* = (0.55 × 2 - 0.45) / 2 = (1.10 - 0.45) / 2 = 0.65 / 2 = 0.325

This suggests betting 32.5% of your bankroll on this trade. If your account is $100,000, the formula recommends risking $32,500 on a single trade. This is insane.

The Kelly formula breaks down for earnings because:

1. Your edge estimate is overstated. You believe you have 55% win rate on your earnings strangle strategy, but you backtested it on data with lookahead bias, didn't account for slippage, and assumed you could always exit at your planned prices. In live trading, the win rate might be 48–50%.

2. Gap risk creates tail risk. The Kelly formula assumes you can only lose your risk amount. On earnings, a gap can lose you 2–3x your planned risk. The formula doesn't account for this.

3. Volatility is temporary. The IV crush that occurs on earnings is mathematically guaranteed. The formula doesn't distinguish between normal market volatility and event-driven volatility that collapses after the event.

4. You don't have infinite capital or infinite time. Kelly formula is optimal for infinitely large accounts over infinite time. For finite accounts that need to survive, the volatility of Kelly sizing is dangerous.

This is why professional traders use half-Kelly or quarter-Kelly, sizing positions at 50% or 25% of the Kelly recommendation. This dramatically reduces volatility and drawdowns while still achieving most of the long-term geometric growth of full Kelly.

The Fractional Risk Model

Most professional earnings traders use fractional risk sizing, which is simpler and more practical than Kelly:

Position Size = (Account Size × Risk Fraction) / Maximum Loss per Unit

For example, if your account is $100,000 and you risk 1% per trade:

Position Size = ($100,000 × 0.01) / $500 = 2 contracts

This means if the trade goes against you and loses the maximum, your account declines by $1,000 (1%).

The key question is: what should the risk fraction be for earnings?

For standard intraday trading, professionals risk 0.5–2% per trade, with 1% being common. For earnings, the risk should be reduced to 0.25–0.75% because of gap risk and execution uncertainty. A conservative trader on an important earnings release might risk only 0.1–0.2%.

The formula above assumes a known maximum loss per unit. For options on earnings, this is easy: the maximum loss on a long option is the premium paid. For short premium positions (strangles, straddles, spreads), the maximum loss is the width of the strikes minus the premium collected—but gap risk can exceed this.

Adjusting for Gap Risk

Gap risk should reduce your position size. The adjustment factor should be based on the stock's historical gap tendency.

Adjusted Position Size = Base Position Size × (1 - Gap Risk Factor)

Where Gap Risk Factor is based on historical data:

• Stable stocks (utilities, consumer staples): 2–3% average gap on earnings. Gap Risk Factor = 0.05–0.10. Reduce position by 5–10%.
• Mid-volatility stocks (industrials, financials): 4–6% average gap. Gap Risk Factor = 0.15–0.25. Reduce position by 15–25%.
• High-volatility stocks (technology, biotech): 7–10%+ average gap. Gap Risk Factor = 0.40–0.50. Reduce position by 40–50%.

For example, if you would normally size a Tesla position (historically 8% gap) at 2 contracts based on 1% risk, you'd reduce it by 40%, resulting in 1.2 contracts (round down to 1 contract in practice).

This adjustment is crude but directionally correct. It forces you to reduce size on the highest-risk trades, which is exactly backward from what most retail traders do.

The Concentration Limit

Another critical sizing rule for earnings: never let a single earnings trade represent more than 5% of your account. Even if the Kelly formula or fractional risk model suggests a larger position, cap it at 5%.

Why? Because earnings trades have tail risk. A massive gap, a liquidity crisis, or a broker's technical failure can cause catastrophic losses that exceed your planned maximum loss. By capping positions at 5%, you ensure that even a 100% loss (total catastrophe, not realistic but possible) will not destroy your account.

Many professional traders use even stricter limits: 2–3% per earnings trade. This seems conservative, but it's insurance against the worst-case scenarios that occur every few years.

Model Comparison: Fixed Contracts vs. Fixed Dollar Risk

Two approaches dominate earnings position sizing:

Approach 1: Fixed Number of Contracts

"I will trade 2 call contracts on every earnings, regardless of the stock's price or volatility."

Advantages: Simple, easy to automate.

Disadvantages: Ignores position sizing best practices. A $300 stock and a $30 stock would be treated identically. Your dollar risk varies wildly.

Verdict: Not recommended. This is how account blowups happen.

Approach 2: Fixed Dollar Risk

"I will risk exactly 1% of my account on every earnings trade, or $1,000 on my $100,000 account."

Advantages: Disciplined, accounts for account growth, properly scales position size.

Disadvantages: Requires recalculation for each trade, still vulnerable to gap risk underestimation.

Verdict: Recommended. This is the professional standard.

The fixed dollar risk approach is mathematically sound and scales naturally. If your account grows to $150,000, your per-trade risk automatically adjusts to $1,500, increasing your per-trade size appropriately. If you suffer a drawdown to $80,000, your risk adjusts downward, protecting capital.

The Pyramid Approach

Some earnings traders use pyramid sizing, where position size increases with confidence levels:

• Low conviction trade (trade idea is unclear, conflicting signals): Risk 0.25% of account. Smallest position size.
• Medium conviction trade (clear setup, mixed market conditions): Risk 0.75% of account. Standard position size.
• High conviction trade (setup is obvious, multiple confirmations): Risk 1.5% of account. Larger position size.

This approach is intuitive: you trade bigger when you're right and smaller when you're unsure. However, it requires honesty about conviction levels. Most traders convince themselves that mediocre trades are high conviction, leading to poor position sizing.

A safer version is:

• Low conviction: 0.25% risk (1/4 size)
• Medium conviction: 0.5% risk (1/2 size)
• High conviction: 0.75% risk (full size)

This caps even high-conviction earnings trades at a manageable 0.75% per trade.

Position Sizing for Different Earnings Strategies

Long Calls or Puts (Directional Bets)

Maximum loss = premium paid. Simple to calculate.

Example: You buy a $105 call for $1.50 on a $100 stock. Maximum loss is $1.50 per share, or $150 per contract (100 shares). If you risk 1% on a $100,000 account ($1,000), you can buy:

Position Size = $1,000 / $150 = 6.67 contracts → 6 contracts

Adjust downward 30% for gap risk on a tech stock:

Adjusted Size = 6 × 0.70 = 4.2 contracts → 4 contracts

Call or Put Spreads (Defined Risk)

Maximum loss = width of strikes minus premium collected.

Example: You buy a 100 / 105 call spread for $0.60, max risk is $4.40 per share = $440 per contract. At 1% risk on $100,000:

Position Size = $1,000 / $440 = 2.27 contracts → 2 contracts

No gap risk adjustment needed because spreads have defined maximum loss (though gap risk can still affect execution price).

Strangles and Straddles (Short Premium)

Maximum loss = width of strikes minus premium collected. However, gap risk is substantial.

Example: You sell a 95 / 105 strangle for $3.00, max theoretical loss is $7.00 per share = $700 per contract. At 1% risk on $100,000:

Position Size = $1,000 / $700 = 1.43 contracts → 1 contract

But gap risk adjustment: reduce by 40% for a volatile stock:

Adjusted Size = 1 × 0.60 = 0.6 contracts → can't trade fractional

This means on a volatile stock, selling strangles at 1% risk becomes impractical. Many traders would either:

• Skip the trade entirely
• Reduce risk per trade to 0.5–0.75%, allowing for 1 contract
• Increase the distance between strikes (wider strangle), reducing the notional risk

This illustrates why short premium strategies on earnings are challenging: the position sizes forced by prudent risk management often become too small to be worthwhile.

Account Simulation: Sizing Multiple Earnings

Suppose your account is $100,000 and you trade 4 earnings in a month at 1% risk per trade. Here's how sizing compounds:

Trade 1 (Apple, risk 1%): $1,000 at risk. You size 4 contracts of $105 calls at $1.50 premium. Stock gaps up 6%, you win $2.50 per contract. Profit: $1,000. Account now $101,000.

Trade 2 (Microsoft, risk 1% of new account): $1,010 at risk. You size 2 contracts of 400 / 405 call spreads at $0.60 premium. Stock barely moves, you lose $600. Profit: −$600. Account now $100,400.

Trade 3 (Tesla, risk 1% of new account): $1,004 at risk, but you only want to risk 0.5% on this one (lower conviction). You size 1 contract of $900 / 910 put spread. Stock jumps 8%, spread expires worthless. Profit: +$400. Account now $100,800.

Trade 4 (Meta, risk 0.75%): $756 at risk. You size 2 contracts of straddle. Stock barely moves, IV crushes. You lose $500. Account now $100,300.

Month Result: Four earnings trades, two winners, two losers, net +$300 on a $100,000 account (+0.3%). Position sizes remained modest, preventing catastrophic loss even on the two losing trades.

This is the power of disciplined position sizing: it keeps you in the game so that positive expected value can compound over time.

Flowchart

Real-world examples

Sizing Microsoft Earnings (April 2024): Your $80,000 account, medium conviction directional call trade. Microsoft historically gaps 3–4% on earnings. You buy $420 calls at $2.00 premium. Max loss per contract = $200.

Base position size = ($80,000 × 0.50%) / $200 = $400 / $200 = 2 contracts

Gap risk adjustment = 2 × 0.95 (5% reduction for MSFT history) = 1.9 contracts

Final size = 1 contract (round down for safety)

Position represents 0.1% of account. Conservative but survivable.

Sizing Tesla Short Strangle (October 2023): $150,000 account, low conviction (conflicting signals). Tesla gaps 8–10% average. You sell 950 / 1050 strangle for $3.50. Max loss = $6.50 per contract = $650.

Base position size = ($150,000 × 0.25%) / $650 = $375 / $650 = 0.58 contracts

This is impractical. You'd skip the trade or:

• Reduce conviction further and don't trade it
• Use a wider strangle (900 / 1100), reducing max loss to maybe $4.00, allowing for 0.93 contracts
• Accept trading 1 contract as 0.43% risk (slightly above 0.25% plan, but acceptable)

Most professionals would skip this trade entirely rather than violate the conviction-sizing alignment.

Sizing Call Spread on Coca-Cola (February 2024): $200,000 account, high conviction based on strong guidance. Coca-Cola gaps 2–3% on earnings. You buy 65 / 70 call spreads for $1.20. Max loss = $3.80 per contract = $380.

Base position size = ($200,000 × 0.75%) / $380 = $1,500 / $380 = 3.95 contracts

Gap risk adjustment = 3.95 × 0.95 (5% reduction for KO history) = 3.75 contracts

Final size = 3 contracts

Position represents 1.14% of account maximum loss. Within acceptable limits.

Common mistakes in earnings position sizing

Mistake 1: Sizing the same across all stocks. A trader buys 1 contract of every earnings, regardless of the stock's gap risk. A stable utility gaps 2% and a biotech gaps 12%, but both get 1 contract. This guarantees poor results because the trader is largest on the most dangerous trades.

Mistake 2: Increasing size on high-probability low-edge trades. A strangle seller finds a trade with 75% probability of profit (high probability) but only 0.5:1 risk-reward (low edge). They size it 3x normal because "the odds are so good." But expected value is negative, and size amplifies the damage.

Mistake 3: Ignoring account recovery math. A trader with $100,000 account takes a $30,000 loss (30% drawdown) on a single earnings trade. They now have $70,000. To get back to $100,000, they need a 43% gain, not 30%. Catastrophic losses are hard to recover from. Smaller positions prevent this.

Mistake 4: Forgetting concentration limits in volatile periods. A trader gets excited about earnings season and trades 3 earnings in one week, each sized at 2% of account. If two go bad, the account is down 4% in days. Concentration limits prevent this.

Mistake 5: Using full Kelly on earnings. A trader calculates their Kelly suggestion as 50% of bankroll, and applies it to earnings trading. One gap move eliminates half the account. Use half-Kelly or quarter-Kelly for earnings, not full Kelly.

Frequently asked questions

What percentage of my account should I risk per earnings trade?

The standard is 0.5–1.0% for experienced traders with robust risk management. Beginners should risk 0.25–0.5%. Conservative traders risk 0.1–0.25%. Never exceed 2% on a single trade, even if you're very confident. The purpose of position sizing is to survive the inevitable losing streaks.

Should I size based on expected value or probability of profit?

Always size based on expected value and maximum loss, not probability of profit. A trade with 75% probability of profit but negative expected value is a loser; don't size it larger. A trade with 40% probability of profit but +$500 expected value is a winner; size it appropriately.

How do I size when I have multiple earnings trades in one week?

Your total allocation for earnings that week should not exceed 5–10% of your account across all positions. If you have four earnings, risk 1–2% per trade, not 3–4%. This prevents concentration risk. Some traders reduce individual position sizes when trading multiple earnings in the same week.

Can I increase position size after I'm already profitable this month?

This is tempting but dangerous. If your account grew 5% this month from winning trades, you might feel confident and trade larger. But the next earnings trade doesn't "know" you're up; it has the same edge (or lack thereof). Maintain consistent position sizing regardless of recent performance. Let position size grow as your account grows, not as your confidence grows.

What if a trade has undefined risk?

Never trade undefined risk on earnings without a hard stop-loss and strict position sizing. Naked short calls or short puts are undefined risk. On earnings, undefined risk becomes catastrophic. Size these as if the maximum loss is the full notional value (e.g., short $100 calls at $100 stock = $10,000 notional risk). This will force positions so small they're not worthwhile, which is the right conclusion.

How do I know if my position size is too large?

If a single losing trade causes you to change your trading plan, reduce position size, or take emotional decisions, it was too large. Your position size should be such that even three consecutive losses are manageable and don't affect your long-term strategy. If a loss makes you want to "revenge trade" to get even, position size was too large.

Related concepts

• Risk-Reward on Earnings Day — Understand the edge before sizing
• The Kelly Criterion and Optimal Sizing — Deep dive into Kelly formula and its limitations
• Managing Concentration Risk — How to avoid over-exposure on single events
• Intraday Risk Management — Position sizing for normal intraday trading
• Account Recovery Math and Drawdowns — Why large losses are hard to recover from
• Earnings Volatility and Gap Risk — Quantifying historical gap risk for different stocks

Summary

Position sizing for earnings is the intersection of position theory and practical risk management. While Kelly criterion and fractional risk models provide the mathematical foundation, earnings require adjustments downward for gap risk, IV crush, and execution uncertainty. Professional traders use 0.5–1.0% fractional risk (with adjustments for gap risk), cap concentration at 5% per earnings trade, and employ half-Kelly or quarter-Kelly sizing rather than full Kelly. The goal is not to maximize profits on each trade but to survive drawdowns and let positive expected value compound over time. Discipline in position sizing is the difference between a career in trading and an expensive learning experience.

Next

→ Using Technical Analysis for Earnings Trades