Learn/The Greeks That Matter/Lesson 2
Lesson 2 of 5

Theta -- Time Is on YOUR Side

What Is Theta?

Theta measures the dollar amount an option's price decreases each day, all else being equal. It is often called 'time decay.' When you sell options, theta is your best friend -- every day that passes erodes the value of the option you sold, bringing you closer to keeping the full premium.

Theta (daily time decay)
Theta = Change in Option Price / Change in Time (per day) | Always negative for long options, positive benefit for sellers

Why Theta Accelerates Near Expiration

Time decay is not linear -- it accelerates as expiration approaches. An option loses a small amount of value per day when it has 45 days to go, but the daily decay ramps up sharply inside of 21 days and becomes most aggressive in the final week. This is why many wheel traders sell options with 30-45 days to expiration (DTE) and close or let them expire around 7-14 DTE, capturing the steepest part of the decay curve.

The Square Root of Time Rule
Time value decays roughly proportional to the square root of remaining time. In practical terms: an option with 4x as much time left does not have 4x the time value -- it has only about 2x. This non-linear decay is why shorter-duration options lose value faster per day.

Theta and Strike Selection

At-the-money (ATM) options have the highest theta because they carry the most extrinsic (time) value. Out-of-the-money (OTM) options have lower absolute theta but higher theta relative to their price. For wheel traders selling OTM puts, the key metric is theta as a percentage of the premium collected -- you want efficient daily decay relative to the risk you've taken on.

Theta in Action
You sell a 30-DTE put for $2.00. Its theta is -0.04, meaning it loses about $4 per contract per day. After 15 days (with the stock unchanged), the option might be worth $1.20 instead of the expected $1.40 (15 x $0.04 = $0.60) -- because theta accelerated as time passed. By day 25, daily decay could be $0.08 or more.

Maximizing Theta as a Wheel Trader

  1. Sell at 30-45 DTE to enter the steepening portion of the decay curve.
  2. Consider closing at 50% of max profit -- this captures the 'easy' theta and avoids gamma risk near expiration.
  3. Avoid selling with less than 14 DTE unless you have a specific, high-conviction thesis -- the premium is thin and gamma risk is elevated.
  4. Stack theta in your favor by staying consistently short premium -- the edge compounds over many trades.
The 50% Rule
Many professional premium sellers close winning trades at 50% of max profit. You capture the fastest theta decay while freeing up capital for the next trade. Empirical backtests show this improves risk-adjusted returns compared to holding to expiration.
Key Takeaways
  • •Theta represents daily time decay -- it works in your favor when you sell options.
  • •Time decay accelerates as expiration approaches, especially inside 21 DTE.
  • •Selling at 30-45 DTE and closing at 50% of max profit captures the most efficient theta.
Quick Check
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An option has a theta of -0.05. Approximately how much value does one contract lose per day?

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