Theta
Daily time decay value
What is Theta?
Theta Theta measures how much an option's price decreases per day due to the passage of time, holding all other variables (stock price, IV, interest rates) constant. A theta of -$0.20 means the option will lose 20 cents in value each calendar day, even if the stock and everything else stays the same. Theta is universally negative for long options — time always erodes time-value. For short options, the equivalent positive theta represents the daily premium accrual that benefits the option seller. This is the mechanical engine behind every premium-selling strategy: time passes, options lose value, sellers profit. Theta is non-linear. It accelerates as expiration approaches, following roughly a 1/sqrt(time) curve. A typical theta profile: - At 60 DTE: theta is small (1-2% of premium per day) - At 30 DTE: theta starts accelerating (2-4% per day) - At 21 DTE: theta is noticeable (3-5% per day) - At 14 DTE: theta enters the steep zone (5-8% per day) - At 7 DTE: theta dominates (8-15% per day) - At 1 DTE (0DTE intraday): theta can be 50-100% of remaining premium per day This accelerating curve is why premium-selling strategies typically focus on the 30-45 DTE entry window with 21 DTE exits. The mid-range captures meaningful theta without the gamma explosion that comes inside 14 DTE. Holding to expiration sounds like "extracting maximum value" but actually trades the steady theta accrual for explosive gamma risk that often turns winners into losers. Theta is not the same for all options at the same DTE. At-the-money options have the highest absolute theta because they carry the most time-value. Deep ITM and deep OTM options have lower theta — ITM options are mostly intrinsic value (which doesn't decay), and OTM options have less time-value to lose. Theta is also why long-options strategies (long calls, long puts, debit spreads) face a structural headwind. The position bleeds value every day. To profit, the directional move must materialize quickly enough to overcome the cumulative theta drag. Many otherwise-correct directional bets lose money because the move took too long.
Complete Definition
Theta measures how much an option's price decreases per day due to the passage of time, holding all other variables (stock price, IV, interest rates) constant. A theta of -$0.20 means the option will lose 20 cents in value each calendar day, even if the stock and everything else stays the same. Theta is universally negative for long options — time always erodes time-value. For short options, the equivalent positive theta represents the daily premium accrual that benefits the option seller. This is the mechanical engine behind every premium-selling strategy: time passes, options lose value, sellers profit. Theta is non-linear. It accelerates as expiration approaches, following roughly a 1/sqrt(time) curve. A typical theta profile: - At 60 DTE: theta is small (1-2% of premium per day) - At 30 DTE: theta starts accelerating (2-4% per day) - At 21 DTE: theta is noticeable (3-5% per day) - At 14 DTE: theta enters the steep zone (5-8% per day) - At 7 DTE: theta dominates (8-15% per day) - At 1 DTE (0DTE intraday): theta can be 50-100% of remaining premium per day This accelerating curve is why premium-selling strategies typically focus on the 30-45 DTE entry window with 21 DTE exits. The mid-range captures meaningful theta without the gamma explosion that comes inside 14 DTE. Holding to expiration sounds like "extracting maximum value" but actually trades the steady theta accrual for explosive gamma risk that often turns winners into losers. Theta is not the same for all options at the same DTE. At-the-money options have the highest absolute theta because they carry the most time-value. Deep ITM and deep OTM options have lower theta — ITM options are mostly intrinsic value (which doesn't decay), and OTM options have less time-value to lose. Theta is also why long-options strategies (long calls, long puts, debit spreads) face a structural headwind. The position bleeds value every day. To profit, the directional move must materialize quickly enough to overcome the cumulative theta drag. Many otherwise-correct directional bets lose money because the move took too long.
Example
A SPY $540 call at 30 DTE typically has theta around -$0.18 per day. Over 7 days, the call loses ~$1.26 in time value even if SPY doesn't move. At 7 DTE, theta accelerates to roughly -$0.45 per day on the same strike.
Related Terms
Frequently Asked Questions
What is theta in options?
Theta measures the daily decay in an option's price due to time passing. Long options have negative theta (lose value each day); short options have positive theta (gain value each day from the seller's perspective).
Why does theta accelerate near expiration?
Theta follows roughly a 1/sqrt(time) curve. The less time remaining, the more sensitive the option price is to each remaining day. At 30 DTE theta is ~3% of premium per day; at 7 DTE it's ~10% per day.
How do options traders profit from theta?
By selling options. Premium sellers collect theta daily as the options they sold decay. Iron condors, credit spreads, covered calls, and cash-secured puts are all theta-positive strategies that generate income as time passes.
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