What is Theta? Time Decay in Options Explained
Understand theta, the Greek that measures time decay in options. Learn why time works against buyers, how theta accelerates near expiration, and strategies to manage it.
Theta
measures how much an option's price decreases each day due to the passage of time, assuming all other factors remain constant. It represents the daily cost of holding an option position.
Theta is always negative for option buyers (time decay costs you money) and positive for sellers (time decay pays you). Theta accelerates as expiration approaches, with the steepest decay in the final 30 days.
Theta = daily time decay cost. A theta of -0.05 means you lose $5/day per contract. Key facts: Theta is always negative for buyers (costs money), positive for sellers (earns money). Decay accelerates in the last 30 days. ATM options have highest theta. Weekends count—options lose time value over Saturday/Sunday. Manage theta by: buying with 45+ DTE, selling with 30-45 DTE, closing before the final week.
What is Theta?
Theta is the Greek that measures time decay—how much value an option loses each day simply from time passing. Every option is a wasting asset: as expiration approaches, the time value component shrinks, eventually reaching zero.
Example: You buy an AAPL $180 call with 30 days to expiration. Theta is -$0.12, meaning the option loses $12 per contract per day. If AAPL doesn't move for 5 days, your option loses approximately $60 in value from theta alone. That's the "rent" you pay for holding the position.
The Theta Decay Curve
Theta doesn't decay linearly—it accelerates. An option loses approximately 1/3 of its time value in the first half of its life and 2/3 in the second half. The steepest decay occurs in the final 2 weeks, which is why professional option sellers target 30-45 DTE to capture the sweet spot of rapid decay.
Practical implication: If you buy options with 60 DTE, theta is manageable—maybe $5-10/day. But that same option at 7 DTE might lose $30-50/day. This is why buying weekly options is so challenging: you're fighting intense theta every hour.
Using Theta to Your Advantage
As a Buyer (Negative Theta)
Buy options with 45-60 DTE to minimize theta drag. Set time-based stop losses: if your thesis hasn't played out by 50% of the time to expiration, consider closing. Never hold purchased options into the final week unless you have a very specific catalyst.
As a Seller (Positive Theta)
Sell options with 30-45 DTE to capture the steepest part of the theta curve. Close at 50% profit and reset. Selling at this timeframe maximizes daily theta collection while avoiding the extreme gamma risk of the final week.
Key Takeaways
- Theta = daily time decay cost (negative for buyers, positive for sellers)
- Decay accelerates in the final 30 days, steepest in the last week
- ATM options have the highest theta—most to lose from time passing
- Buyers: use 45-60 DTE to minimize theta drag
- Sellers: target 30-45 DTE to maximize daily theta collection
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