Theta Decay & Time Value
Greeks
Key Takeaways
- Extrinsic (time) value decays to zero by expiration. This is what sellers harvest.
- Decay accelerates in the final 2 weeks, making 30-45 DTE the ideal selling window.
- Close winners at 50% profit to capture the bulk of theta without enduring the risky final stretch.
TL;DR
Time value (extrinsic value) is the portion of an option's premium that decays daily. For sellers, this decay is profit. The decay curve is exponential: slow at first, then rapid in the final weeks. Sell at 30-45 DTE and close at 50% profit to maximize the decay/risk ratio.
How Time Destroys Option Value
Every option has a built-in countdown clock. As expiration approaches, the extrinsic (time) value of the option decays toward zero. At expiration, only intrinsic value remains.
For a $50 call when the stock is at $48:
- 45 DTE: premium might be $3.00 (all extrinsic)
- 30 DTE: $2.20
- 15 DTE: $1.20
- 7 DTE: $0.50
- Expiration: $0.00
As a seller, you collected $3.00 and it decayed to zero. That's $300/contract of pure income.
The Decay Curve Is Not Linear
Theta decay follows an exponential curve: slow at first, then accelerating rapidly in the final weeks.
Roughly:
- Days 45-30: ~15% of extrinsic value decays
- Days 30-15: ~35% of extrinsic value decays
- Days 15-0: ~50% of extrinsic value decays
This means the last two weeks destroy more value than the first month combined. This is why selling 30-45 DTE is optimal. You're entering right as the acceleration begins.
Why 50% Profit Targets Work
If you sell an option for $3.00 and close at $1.50 (50% profit), you've captured $150 in roughly half the time. Why not wait for 100%?
Risk/reward flips after 50%. To capture the remaining $1.50, you'd wait another 2-3 weeks while gamma risk increases. A sudden stock move in the final week can erase all your gains.
Capital efficiency. Closing early frees up capital and margin for a new trade. Two 50% winners in the same period often earn more than one 100% winner.
Theta Decay by Strike
Not all options decay at the same rate:
ATM options have the highest theta. They have the most extrinsic value to lose.
Deep OTM options have low theta in absolute terms but can lose a high percentage of their value quickly.
ITM options also have lower theta since much of their value is intrinsic (which doesn't decay).
For premium sellers, this means ATM and slightly OTM options (0.25-0.35 delta) capture the most theta decay per day.
Weekend and Overnight Decay
Theta doesn't stop on weekends. An option expiring in 30 calendar days is really 22 trading days. The market prices theta continuously, which means you're earning decay income on Saturdays, Sundays, and holidays.
Selling on Friday afternoon and buying back Monday morning can sometimes capture noticeable decay with minimal stock-move risk, especially for options with < 14 DTE.
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