Theta measures time decay—how much an option’s value decreases each day as expiration approaches. Theta is expressed as a negative number for long options (they lose value) and positive for short options (decay benefits sellers). Theta decay accelerates as expiration nears, making it a critical factor for options traders.
- Measures daily time decay in dollars
- Negative for buyers (lose daily), positive for sellers
- Decay accelerates near expiration
How Theta Works
Theta erodes option value daily:
Theta Decay Example:
Option: ATM call, 30 days to expiry
Premium: $4.00
Theta: -0.08
Day 1: $4.00
Day 2: $3.92 (lost $0.08)
Day 3: $3.84 (lost $0.08)
As expiration nears, theta increases:
Day 20: Theta becomes -0.12
Day 25: Theta becomes -0.18
Day 29: Theta becomes -0.25
Decay accelerates dramatically in final weeks!
Quick Reference: Theta by Time
| Days to Expiry | Theta Speed | Daily Decay |
|---|---|---|
| 90+ days | Slow | Minimal |
| 60-90 days | Gradual | Low |
| 30-60 days | Moderate | Noticeable |
| 14-30 days | Fast | Significant |
| 0-14 days | Very Fast | Aggressive |
Example: Theta Impact
30-Day Option Decay:
| Day | Premium | Theta | Daily Loss |
|---|---|---|---|
| 30 | $5.00 | -0.08 | $8/day |
| 20 | $4.10 | -0.10 | $10/day |
| 10 | $2.80 | -0.15 | $15/day |
| 5 | $1.60 | -0.22 | $22/day |
| 1 | $0.40 | -0.40 | $40/day |
Time decay is not linear—it accelerates.
Theta measures how much an option loses daily to time decay. Buyers lose to theta; sellers profit from it. Decay is slow at first but accelerates dramatically in the final weeks before expiration. Manage theta by timing your trades carefully.
Theta by Moneyness
| Option Type | Theta Level | Reason |
|---|---|---|
| ATM | Highest | Most time value to decay |
| ITM | Lower | Less time value |
| OTM | Lower | Less time value |
ATM options have the most time value, so they have the most to lose.
Managing Theta
For Buyers
- Give yourself enough time (60+ days)
- Don’t hold too long—take profits
- Avoid holding into final 2 weeks if possible
For Sellers
- Sell options to collect theta
- 30-45 days to expiration is sweet spot
- Theta accelerates in your favor near expiry
Theta Strategies
Theta-Positive (Sellers)
- Covered calls
- Cash-secured puts
- Iron condors
- Credit spreads
Theta-Negative (Buyers)
- Long calls/puts
- Debit spreads
- Straddles/strangles
Common Mistakes
-
Holding options too long – Theta erodes profits. Take profits early.
-
Buying weeklies without quick thesis – Extreme theta decay.
-
Not factoring theta into breakeven – Need bigger moves to overcome decay.
-
Ignoring weekends – Some models show theta decaying over weekends too.
How JournalPlus Tracks Theta
JournalPlus tracks theta exposure for your options portfolio, showing daily decay and helping you time entries and exits to manage time decay effectively.
