Understanding Options Greeks - Delta, Theta, Vega and Gamma Explained
Options Greeks are the sensitivity measures that quantify how an option's price changes in response to different factors: stock price movement, time passing, volatility changes, and interest rate changes. For wheel strategy traders who sell cash-secured puts and covered calls, understanding Greeks — especially delta and theta — is essential for selecting the right strikes, managing position risk, and timing entries and exits effectively.
Delta measures how much the option's price moves for each one-dollar change in the underlying stock price. For options sellers, delta also serves as an approximate probability of the option expiring in-the-money. Selling a 0.30-delta put means the market prices approximately a 30 percent chance of assignment — this is the standard starting point for the wheel strategy because it balances premium income against manageable assignment risk.
Theta represents the daily time decay of an option's value. As an options seller, theta works in your favor — every day that passes without an adverse stock move puts more premium in your pocket. At-the-money options have the highest theta decay, but also the highest assignment risk. Out-of-the-money options decay more slowly but offer lower absolute premium. Vega measures sensitivity to implied volatility changes — when volatility rises, option prices increase, which hurts your position value as a seller even if the stock price has not moved adversely. Understanding vega helps you time entries around volatility events like earnings announcements.