How fast does theta affect option price?

Answered by Ricardo McCardle

Theta, also known as time decay, plays a crucial role in the pricing dynamics of options. It represents the rate at which the value of an option erodes as time passes. In essence, theta quantifies the daily decrease in the price of an option.

The impact of theta on option price varies depending on several factors, such as the time to expiration, the volatility of the underlying asset, and the strike price of the option. Generally, theta is smaller further away from the expiration date and accelerates more rapidly as expiration approaches.

To illustrate this, let’s consider an example. Suppose you hold an option with a theta value of -0.02. This means that the option will lose $0.02 (or $2) in value per day. If you hold the option for ten days, the total decrease in value due to theta would be $0.02 * 10 = $0.20 (or $20).

It’s important to note that theta is not constant throughout the life of an option. Its magnitude increases as expiration approaches. This is because the time value of an option diminishes as it gets closer to expiration, as there is less time for the underlying asset to make a significant move in favor of the option holder.

As expiration nears, the rate of time decay accelerates, resulting in a steeper decline in the option’s price. This phenomenon is particularly evident in options with a shorter time to expiration. Therefore, options that are close to expiration experience a more pronounced impact from theta compared to options with a longer time horizon.

Additionally, theta is influenced by the volatility of the underlying asset. Higher implied volatility generally leads to higher option premiums, as there is a greater likelihood of significant price movements. Consequently, options with higher volatility tend to have larger theta values, as there is more uncertainty and potential for price changes in the remaining time until expiration.

Theta represents the daily decrease in the price of an option due to time decay. Its impact on option price is not constant but rather accelerates as expiration approaches. Understanding theta is essential for option traders, as it helps them assess the potential erosion of an option’s value over time and make informed decisions regarding their trading strategies.