Time Decay of Options: How It Works & Its Importance

By Brian Nibley · May 18, 2024 · 6 minute read

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Time Decay of Options: How It Works & Its Importance


Editor's Note: Options are not suitable for all investors. Options involve risks, including substantial risk of loss and the possibility an investor may lose the entire amount invested in a short period of time. Please see the Characteristics and Risks of Standardized Options.

Time decay, as it relates to options trading, has to do with an option contract’s loss of value as it nears its expiration date. There are numerous variables in the mix when it comes to time decay, but knowing the basics of what the terms means, and how it can affect an investment strategy, can be important for investors.

Key Points

•   Time decay refers to the reduction in an option’s value as its expiration date approaches.

•   The rate of time decay is represented by theta, which accelerates as expiration nears.

•   Options lose more value in the final month before expiration due to increased time decay.

•   Intrinsic and extrinsic values are key components in options pricing, affected by time decay.

•   Understanding time decay is crucial for options traders to manage potential profits and losses effectively.

What Is Time Decay?

Time decay is the loss of an option’s value as it gets closer to expiration. An option’s time value refers to the extent to which time factors into the value — or the premium — of the option. Time decay accelerates, or declines more quickly, as the expiration date gets closer because investors have less time to exercise the contract.

For options traders, understanding the power of time decay is important whether you’re buying call options or put options. Here are the basics you need to know.

Recommended: Options Trading: A Beginner’s Guide

How Time Decay Works

The rate of change in the time value of an option is known as theta. For traders who buy options with the intention of holding them until expiration, theta usually isn’t of great concern. That’s because traders who hold contracts until the expiry date are hoping that the underlying security moves so far in their favor that the reward in terms of intrinsic value will outweigh any loss in extrinsic value.

But traders who want to close their options position prior to expiration may be more concerned about time decay. Because the security will have less time to move in their favor, the potential profit from intrinsic value is reduced, and the potential loss of extrinsic value becomes greater.

While both intrinsic and extrinsic value are important for options traders of all kinds, the type of options trading strategy a trader is using can influence which factors they put more emphasis on.

Understanding Options Pricing

Time decay isn’t a difficult concept, but it does require a quick refresher about how options are traded and priced.

Four of the main variables that impact the price of an option are:

1.    The underlying price and strike price

2.    Time left until expiration

3.    Implied volatility

4.    Time decay

The underlying price, strike price, and expiration date of the options contract are the main factors that determine its intrinsic value, while implied volatility and time decay are the factors that determine its extrinsic value.

•   Intrinsic value. An option’s intrinsic value refers to the option’s value at the time of expiration, which depends on the price of its underlying security relative to the strike price of the contract. In other words, whether the option is in the money, out of the money, or at the money.

•   Extrinsic value. Extrinsic value refers to how time can impact the option’s value, i.e. its premium. As the expiration date of the options contract approaches, there’s less time for an investor to profit from the option, so time decay or theta, accelerates and the option loses value.

Interest rates can also affect options prices, but this is more of a macro factor that doesn’t have to do with the specific contract itself.

Thus, time value represents the added value an investor has to pay for an option above the intrinsic value. Options are sometimes referred to as depreciating or wasting assets because they tend to lose value over time, since the closer the option is to expiration, the faster its time value erodes.

Recommended: Popular Options Trading Terminology to Know

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How to Calculate Time Decay

The rate of an option’s time decay is measured by theta.An option with a theta of -0.05 (theta is expressed as a negative value) would be expected to fall about $0.05 each day until expiration, but this would likely accelerate during the days and weeks leading up to the expiry date.

Greek values like theta are constantly changing, and can therefore be one of the most difficult factors to take into account when trading options.

Example of Time Decay of Options

Imagine an investor is thinking about buying a call option with a strike price of $40. The current stock price is $35, so the stock has to rise by at least $5 per share for the option to be in the money. The expiration date is two months in the future, and the contract comes with a $5 premium.

Now imagine a similar contract that also has a strike price of $40 but an expiration date that is only one week away and comes with a premium of just $0.50. This contract costs much less than the $5 contract because the stock would have to gain almost 15% in value in one week to make the trade profitable, which is unlikely.

Thus, the extrinsic value of the second option contract is lower than the first, because of time decay.

How Does Time Decay Impact Options?

Option time decay is pretty straightforward in principle. Things can be more complicated in practice, but in general, options lose value over time. The more time there is between now and the expiry date of the option, the more extrinsic value the option will have. The closer the expiry date is to the current date, the more time decay will have taken effect, reducing the option’s value.

The basic idea is that because there’s less time for a security to move one way or the other, options become less valuable the closer they get to their expiration dates. This isn’t a linear process though. The rate of time decay accelerates over time, with the majority of decay occurring in the final month before expiration.

💡 Quick Tip: How to manage potential risk factors in a self-directed investment account? Doing your research and employing strategies like dollar-cost averaging and diversification may help mitigate financial risk when trading stocks.

The Takeaway

If you think about it, the time value of an option is similar to other things that have a value which is time dependent. A fresh loaf of bread, a new car, a newly built home — these items would have an intrinsic value, but you might also pay a premium when they’re at full value.

As time passes, though, consumers will pay less for loaf of bread that isn’t fresh — or a car or home that’s older — because time has eroded some of the value. Similarly, as an option gets closer to its expiration date, it too loses value owing to the effects of time decay or theta.

Qualified investors who are ready to try their hand at options trading, despite the risks involved, might consider checking out SoFi’s options trading platform. The platform’s user-friendly design allows investors to trade through the mobile app or web platform, and get important metrics like breakeven percentage, maximum profit/loss, and more with the click of a button.

Plus, SoFi offers educational resources — including a step-by-step in-app guide — to help you learn more about options trading. Trading options involves high-risk strategies, and should be undertaken by experienced investors.

For a limited time, opening and funding an Active Invest account gives you the opportunity to get up to $1,000 in the stock of your choice.


Photo credit: iStock/Tatyana Azarova

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