How option price is calculated depends on a variety of factors, Pricing Models, Intrinsic Value, and Extrinsic Value.
Option Pricing Models Before venturing into the world of trading options, investors should have a good understanding of the factors determining the value of an option. These include the current stock price, the intrinsic value, time to expiration or the time value, volatility, interest rates, and cash dividends paid.
There are several options pricing models that use these parameters to determine the fair market value of an option. Of these, the Black-Scholes model is the most widely known.1 In many ways, options are just like any other investment—you need to understand what determines their price to use them effectively. Other models are also commonly used, such as the binomial model and trinomial model.
Let's start with the primary drivers of the price of an option: current stock price, intrinsic value, time to expiration or time value, and volatility. The current stock price is fairly straightforward. The movement of the price of the stock up or down has a direct, though not equal, effect on the price of the option. As the price of a stock rises, the more likely it is that the price of a call option will rise and the price of a put option will fall. If the stock price goes down, the reverse will most likely happen to the price of the calls and puts.
Intrinsic Value Intrinsic value is the value any given option would have if it were exercised today. Basically, the intrinsic value is the amount by which the strike price of an option is profitable or in-the-money as compared to the stock's price in the market. If the strike price of the option is not profitable as compared to the price of the stock, the option is said to be out-of-the-money. If the strike price is equal to the stock's price in the market, the option is said to be "at-the-money."
Although intrinsic value includes the relationship between the strike price and the stock's price in the market, it doesn't account for how much (or how little) time is remaining until the option's expiration—called the expiry. The amount of time remaining on an option impacts the premium or value of an option, which we'll explore in the next section. In other words, intrinsic value is the portion of an option's price not lost or impacted due to the passage of time.
Time Value Since options contracts have a finite amount of time before they expire, the amount of time remaining has a monetary value associated with it—called time value. It is directly related to how much time an option has until it expires, as well as the volatility, or fluctuations, in the stock's price.
The more time an option has until it expires, the greater the chance it will end up in the money. The time component of an option decays exponentially. The actual derivation of the time value of an option is a fairly complex equation.
In other words, the time value is what's left of the premium after calculating the profitability between the strike price and stock's price in the market.
As a result, time value is often referred to as an option's extrinsic value since time value is the amount by which the price of an option exceeds the intrinsic value. Time value is essentially the risk premium the option seller requires to provide the option buyer the right to buy or sell the stock up to the date the option expires. It is like an insurance premium for the option; the higher the risk, the higher the cost to buy the option.
As a general rule, an option will lose one-third of its value during the first half of its life and two-thirds during the second half of its life. This is an important concept for securities investors because the closer the option gets to expiration, the more of a move in the underlying security is needed to impact the price of the option.