Trading Earnings with Straddles: When to Buy and When to Sell

A straddle consists of buying or selling both a call and a put at the same strike price and expiration. Around earnings, straddles become the purest expression of a volatility bet. Buying a straddle profits when the stock moves more than the straddle price in either direction. Selling a straddle profits when the stock moves less than the premium collected. The decision to buy or sell comes down to one question: is the market overpricing or underpricing the expected move?

To answer this question, build a simple model comparing the implied move to the historical move. Calculate the implied move by taking the price of the at-the-money straddle for the nearest expiration after earnings and dividing by the stock price. Then pull the actual post-earnings moves for the last eight to twelve quarters. If the average realized move exceeds the implied move, the straddle is underpriced and buying has an edge. If the implied move exceeds the average realized move, the straddle is overpriced and selling has an edge. Studies consistently show that, on average across the market, straddles are slightly overpriced, which is why selling earnings straddles has a positive expected value over large sample sizes.

However, averages mask significant variation. Some stocks consistently move more than implied, such as high-growth names with volatile earnings surprises, while others consistently move less than implied, such as stable blue chips with predictable results. Track each stock's historical implied-vs-realized move ratio to identify which category it falls into. A stock that has beaten its implied move in seven of the last eight quarters is a better candidate for a long straddle, while one that has stayed within the implied range eight out of eight times is a strong candidate for a short straddle.

Risk management for earnings straddles requires accepting that any single trade has a wide range of outcomes. Position size conservatively: allocate no more than 2% to 3% of your portfolio to any single earnings straddle. For short straddles, always define your risk by converting to an iron butterfly, which adds long wings to cap your maximum loss. For long straddles, accept that the premium paid is your maximum risk and that you need a significant move to profit. Close long straddles the morning after earnings if the move has not materialized, rather than holding and hoping, because theta decay will rapidly erode any remaining value.