What is theta?
Theta measures how much an option's price decreases each day, all else being equal. A theta of -0.05 means the option loses $5 per contract per day purely from the passage of time. For options sellers, theta is income — every day that passes quietly puts money in your pocket because the option you sold becomes cheaper to buy back.
Why theta decay is not linear
Theta decay accelerates as expiration approaches. An option with 60 days to expiration might lose $2/day, while the same option with 10 days left could lose $8/day. Roughly one-third of an option's time value erodes in the final third of its life. This is why premium sellers typically enter at 30-45 DTE — they capture the acceleration zone without the extreme gamma risk of the final week.
Theta and moneyness
At-the-money (ATM) options have the highest theta because they have the most time value to lose. Out-of-the-money (OTM) options — the typical choice for premium sellers — have less theta per dollar but a higher probability of expiring worthless. The sweet spot for premium selling is typically 15-30 delta, where theta is meaningful and probability of profit is above 70%.
Theta across strategies
Short put: Positive theta, profit from time decay on one leg. Credit spread: Lower theta than a naked put but capped risk. Iron condor: Collects theta from both sides — double the time decay but double the gamma risk. Short strangle: Maximum theta collection but undefined risk on both sides. Your strategy choice determines how much theta you harvest and how much risk you accept.
Maximizing theta in practice
To maximize theta decay: sell when IV Rank is high (higher premium = more theta). Enter at 30-45 DTE to capture the acceleration curve. Take profits at 50% of max to avoid gamma risk near expiration. Avoid earnings within your DTE window — the theta "runway" gets disrupted by vol events. Use the Strategy Builder to compare theta across strategies before entering.
When theta works against you
Theta is only your friend when the stock stays within your expected range. A large directional move can overwhelm days or weeks of theta decay in hours. This is why premium sellers pair theta strategies with proper strike selection (outside the expected move), position sizing (1-3% of portfolio per trade), and management rules (close at 50% profit or 2x loss).