What Is Options Theta?
Theta measures how much an option loses in value each day simply from the passage of time. It's the enemy of option buyers and the best friend of option sellers.
Definition
Theta is the daily rate at which an option loses value due to time passing — all else being equal. A theta of -0.05 means the option loses $0.05 per share ($5 per contract) every day. This decay accelerates as expiration approaches, hitting its fastest in the final week.
Theta is always negative for option buyers (you lose value daily) and positive for option sellers (you gain that decay as profit). This is why selling options is sometimes described as 'collecting theta' — you profit from time passing, not from predicting direction.
At-the-money options have the highest theta, losing the most value daily. Deep ITM and deep OTM options have lower theta. Weekly options have very high theta decay rates (must decay to zero in 7 days vs 30), which is why selling weekly options is a popular income strategy.
Real-World Example
You buy an ATM call with theta of -0.08. Over a weekend (3 calendar days, but theta accounts for weekends), your option loses $0.24 per share ($24 per contract) from time decay alone — even if the stock doesn't move at all.
Why It Matters
Theta is the silent killer for option buyers — even when you're right about direction, time decay can erode your gains. Understanding theta is essential for choosing the right expiration and strategy.
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Frequently Asked Questions
How do I avoid theta decay as an option buyer?
Buy options with more time to expiration (LEAPS) to reduce daily theta impact. Avoid holding options through the final 2 weeks before expiration when decay accelerates most. Or switch to selling strategies where theta works for you, not against you.
Is selling options always better than buying because of theta?
Theta favors sellers statistically, but sellers also face larger potential losses. A sold put can lose multiples of the premium collected if the stock crashes. Theta advantage must be weighed against the risk of large adverse moves.
Does theta decay over weekends?
Yes — brokers charge 3 days of theta for Friday-expiring options held over the weekend (Friday close to Monday open). The market is closed but the calendar advances, so time value decays. This is why some traders close positions on Fridays.
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